Symposium 345 - Poster Abstracts


The action of gaseous matter and the principle of the formation of two stars

Zhang, Man Ping

[The effect of the atmosphere on celestial bodies] I think the two with the atmosphere of the celestial bodies in the universe when they met the first contact with the earth's atmosphere can not directly collided, two objects to collide with the atmosphere conditions must be away the atmosphere, (two celestial atmosphere contact gravity is less than the attraction of two objects themselves for gas, two gas own gravity cannot both unity) between the two objects at a distance to meet the need of gravity away atmosphere to make two gas both unity can collide, push not collided atmospheric walk or not. Don't ignore the atmosphere that is depends on how much is the content of the atmosphere, atmosphere and material away it needs power, such as the atmosphere around the earth to the other half the ball to the other half of the ball pressure will increase by resistance, so the atmosphere is two celestial body resistance (mutual gravity when the two objects and two celestial atmosphere to the resistance of the force balance) between two objects distance on the force balance neither close to or separate, two celestial atmosphere in the form of a sphere contact form binary phenomenon. Binary stars are captured and formed when the third and more objects are captured. (a two-star phenomenon must be a celestial body with an air layer, and a small object with no air layer is directly into any object that has an atmosphere.

Chemical reactions in interstellar medium

Chen, Tao

Polycyclic aromatic hydrocarbon (PAH) molecules are an important component of the interstellar medium (ISM) locking up ~10% of the elemental carbon. Understanding their characteristics and their dependence on local physical conditions is crucial in astrophysics. Interstellar PAHs are assumed to form in processes akin to soot formation in the cooling ejecta of carbon-rich Red Giant stars as they flow from the stellar photosphere into the ISM. Subsequently, they are further processed for millions of years by photons of the interstellar radiation field. Driven by this astrophysical interest, large number of experiments and theoretical studies focusing on the reactions of PAHs have attracted much interest in recent years. Different processes are investigated, varying from sequential fragmentation, isomerization, ionization and molecular growth processes. Dedicated studies of the involved dissociation channels provide information on the molecular dynamics at play and this is interesting, both from an astronomical and physical chemical point of view. Particularly processes changing the nature of the carbon skeleton have been the topic of recent studies. In photodissociation regions in space, (large) PAHs (with more than 50 C-atoms) are considered starting points in the formation of other species, including fullerenes, carbon cages and smaller hydrocarbon chains. PAHs with functional side groups may also be important. Inside molecular clouds, PAHs are expected to be trapped in low temperatures (∼10 K) ice mantles, consisting mainly of H2O with traces of CH3OH, CO2, CO, and NH3. Photolysis of these complex ice mixtures is known to functionalize PAHs with alcohol, ketone, amino, methyl, methoxy, cyano/isocyano, and carboxyl groups, which is crucial for formation of complex organic molecules and enrichment of the molecular inventory in space. _x000D_ In this work, we review the recent experimental and theoretical studies on chemical reactions of the interstellar PAHs.

Electromagnetic induction heating of planets orbiting late M dwarfs

Kislyakova, Kristina

We present our results on the induction heating of planetary interiors inside planets orbiting late type M dwarfs with strong magnetic fields. Induction heating arises when the conducting body (in this case, an exoplanet with a conducting mantle) is embedded into constantly varying magnetic field. We consider two cases: in the first one, the planet is supposed to orbit in its host star’s equatorial plane and the varying magnetic field at planetary orbit arises due to an inclination between the stellar magnetic dipole and stellar rotation axis. In the second case, we assume the two axes of the stellar magnetic dipole and the stellar rotation to be coalighned and study induction heating inside planets orbiting on inclined orbits. Our calculations show that induction heating can in some cases melt the upper mantle and enormously increase volcanic activity, sometimes producing a magma ocean below the planetary surface. This conclusion is very important for the planetary habitability, because it influences the outgassing and, thus, also the atmospheric composition of a planet in the habitable zone. It is also important for close-in planets, as induction heating can be very strong close to a star and exceed the energy release inside the Jupiter’s satellite Io, likely leading to a fully molten mantle of such planets and totally changing the energy budget of planetary mantle and planetary interior evolution.

Phenomenon of the wave ordering and the diagram "mean density - global period" in the Solar planetary system

Skulskyy, Mykhaylo

The study of wave and gravitational factors that reflect the spatial characteristics of the Solar planetary system was conducted._x000D_ It is proved that the spatial structure of the Solar system can be reflected in two related algorithms of the same wave mechanism. The outer planets are located at distances from the Sun in accordance with a certain length of the standing wave. This algorithm is also valid and for well-known dwarf planets and comet families. The algorithm of the inner planets is ordered by the dependence in which the lengths of their orbits are in proportion to the same length of standing wave or its harmonics._x000D_ At the same time, it is detected that such a wave-space structure of the Solar System is connected to the global oscillations of the planets and Sun as a whole.This detected coherence of their global oscillations was studied taking into account the most massive satellites of planets and dwarf planets. All main objects of the Solar system have formed a clear functional relations between the periods of their global oscillations and their mean densities. Graphically, it is represented as a diagram "mean density - global period" which shows the ability of the self-organization in Solar planetary system. In particular, the planets and other groups of objects on this diagram are discretely ordered and the locations of many massive satellites of the planets are due to the effects of tidal forces._x000D_ Overall, the wave and gravity factors are represented in obvious interrelations and create an indivisible natural phenomenon. This generalized phenomenon does not look accidental leaving open the question of its origin and formation in the Solar planetary system and the options for its interpretation._x000D_ Key words: Solar system structure, wave ordering, means densities, global oscillations

A conception of proto-sun disk with high angular momentum evolution

Bagrov, Alexander V.

The Standard Planetary Cosmogony describes the evolution of protoplanetary nebula that remained near the young Sun. Its specific angular momentum j must be less than rotation stability limit for a single star with mass M¤: j ≤ 1.7·1017(M/M¤)2/3 cm2·s-1. On the other hand, minimal angular momentum required for the creation of a double star is 10 times more. When the specific angular momentum of the protostellar nebula is slightly less than j ≤ 1.7·1018(M/M¤)2/3 cm2·s-1, rotation of the nebula will stop its accretion to the center before the gathered mass will be enough to become a star. In this case, the protostellar nebula turns into a flat rotating disc. Dust particles in the disc will play a role of an effective refrigerator, so all material of the disc has to be cold. Gases in the disc will stop turbulence, so all particles will be on circular Keplerian orbits. All particles will have nearly exact Keplerian velocities with negligible differences produced by temperature. This will lead to a diffusion shift of low-speed particles to the center of the protostellar disc. So the mass of the central part of the disc will be steadily increasing without acquiring angular momentum. Eventually, the concentrated mass will be enough for producing a star, and the opacity of the central gaseous globe will lead to the heating of its inner part, which is necessary for the nuclear synthesis. Hence a star in the center of a fast rotating disk will have long rotation period.

Interstellar striders as migrating bodies through planetary systems

Bagrov, Alexander V.

In 2011 at least 10 “free-floating planets” with roughly the mass of Jupiter were detected with gravitational microlensing. October 19, 2017, using the Pan-STARRS1 telescope in Hawaii astronomers discovered a small “interstellar strider” named ‘Oumuamua that crossed our Solar system luckily near to the Earth to be detected by survey telescope. Taking in account sensitivity of the telescope, visible velocity of the discovered object and a volume of space, where it was detected, the researchers supposed that such an interstellar body can penetrate into an inner part of the Solar system each year._x000D_ There are many reasons to believe that in the interstellar space may exist bodies much larger than ‘Oumuamua, though they will occur rarer. This assumption automatically will lead to a simple idea, that some of the interstellar striders can collide with bodies of our planetary system. If interstellar striders are “primordial” planetezimales lost by extrasolar planetary systems, they are ordinary comet nuclei that consist of frozen volatiles and dust. When they hit, say, the Earth, they can produce large flat collision craters (“astroblems”). All volatiles from the hitter will totally evaporate, and dust particles from comet nucleus will be the same as the dust of Earth soil. So no footprints of interstellar origin of hazardous hitter will be preserved. If 10-km sized interstellar strides are 100 times less rare than 1-km ‘Oumuamua, the probability of their direct collision with the Earth will be about 1 event in 100000 years. It may be only coincidence, but the time between the appearance of huge astroblems on the Earth surface is about 100000 years too. Hence we may suppose that interstellar striders play their own role in the evolution of the Solar planetary system.

Main pileup in exoplanet period distribution is double-peaked, being separated by a gap, for planets of metal-rich sunlike single stars

Taylor, Stuart F.

We present major new features in the log period distribution of the counts of a primary population of planets, those 40% of planets hosted by stars that are metal-rich and sunlike in surface gravity: The main pileup of these planets’ distribution in log period that broadly peaks at several hundred day periods is composed of not one but two peaks, with a prominent gap separating these two peaks. This double-peaked shape is unexpected, and is not present in the periods of planets of the main other populations of stellar hosts: Stars with low surface gravity, and metal-poor sunlike stars. The gap is at least partially absent for periods of planets of sunlike stars with stellar companions. These readily verifiable features appear important to the how distribution of eccentricities by period shows a correlation with metallicity at shorter periods that goes away in the gap region where the metal-poor population peaks. This correlation appears to more weakly come back in the period range of the longer period peak. We discuss how other parameters vary in the short period peak, gap, and long period peak regions.

New eyes on planet-disk interactions

Bertrang, Gesa H.-M.

The circumstellar disk around the Herbig Ae/Be star HD169142 is a well-studied object which shows structures on multiple wavelength ranges. Moreover, HD169142 harbors the most promising proto-planet candidate._x000D_ We present new SPHERE/ZIMPOL data which distinctly deviate from the established picture developed for this object. Based on these new observations as well as high-resolution ALMA observations and further archival data, we built a new model for this disk. These new eyes, namely SPHERE and ALMA, in combination with 3D radiative transfer simulations strongly indicate that we are witness to previously undetected planet-disk interactions in HD169142.

Growing up in a rougher neighbourhood: Star and planet formation/evolution in extreme environments

Longmore, Steven

Our understanding of star and planet formation is underpinned by observations of systems forming close to Earth at the present day. However, most stars in the Universe (including our own Sun) formed at earlier epochs of the Universe, when the properties of the interstellar medium were very different. Understanding how stars and planets form and evolve in gas with densities, temperatures, and pressures orders of magnitudes higher than in the local universe is therefore fundamental to linking formation theories to the observed (extrasolar) planet population. In our lifetime no observational facilities will have sufficient sensitivity and resolution to observe individual forming stars/planets at the epoch of peak star formation (z=1-2). However, the properties of gas in the inner few hundred parsecs of our Galaxy are remarkably similar to gas in galaxies at this epoch. At only a fraction of the distance to high redshift galaxies, the Galactic Centre molecular clouds therefore offer an ideal laboratory for understanding star and planet formation/evolution in more extreme environments. Over the last few years we have undertaken a systematic ALMA study to trace the gas in extreme Galactic Centre molecular clouds down to the size scales of individual forming stars and proto-planetary disks (<1000AU). I will summarise the results from these observations aiming to quantify the differences in star/planet formation and chemistry in this environment compared to that in nearby clouds.

Gaseous clumps, accretion bursts, and the prospects of giant planet formation in gravitationally unstable protostellar disks

Elbakyan, Vardan

Planets form in gaseous and dusty disks around young stars. A possible scenario for giant planet formation is disk gravitational instability and fragmentation. We use high-resolution grid-based numerical hydrodynamics simulations to compute the formation and long-term evolution of gravitationally unstable protostellar disks around solar-mass stars. We show that gaseous fragments that have formed in the outer regions of a protostellar disk (> 100 AU) through disk fragmentation may later become perturbed by other fragments or disk structures, such as spiral arms, and quickly migrate toward the central star (during ~ few 103-104 years). During inward migration, the fragments first gain mass (up to several tens of Jupiter mass), but then quickly lose most of it through tidal torques when approaching the star. Part of the lost material can be accreted on the central star causing an FU-Ori-type luminosity outburst. This mass loss, or tidal downsizing, helps the fragments to halt their inward migration at a distance of a few tens of AU. The resulting fragments are heavily truncated both in mass and size compared to their wider-orbit counterparts, keeping only a dense and hot nucleus. During the inward migration, the central temperature in these fragments may exceed the molecular hydrogen dissociation limit (~2000 K) and the central region of the fragment can collapse into a gas giant protoplanet. We argue that FU-Orionis-type luminosity outbursts may be the end product of disk fragmentation and inward fragment migration, ushering the formation of giant protoplanets in the inner parts of protostellar disks.

Planetary Magnetism as a Factor of Exoplanet Habitability

McIntyre, Sarah

Discovering life outside the solar system using telescopic observations is the ultimate goal of planetary science. However, while we wait for the next generation of telescopes to come online, we can make use of current data to assess the habitability of a planet using a variety of planetary and astronomical features. This will assist in determining optimal targets for near-future observations of planetary atmospheres.One requirement for habitability is liquid water. Thus far this requirement has only been applied to determining the location of the circumstellar habitable zone (CHZ). However, a strong dipolar magnetic moment may play a significant role in the maintenance of an atmosphere and surface liquid water. Mars’s weak magnetic field is thought to have contributed to the loss of atmosphere and ultimately the absence of liquid water on its surface today. Furthermore, the high D/H abundance ratio in the atmosphere of Venus (120 times that on Earth) indicates large amounts of water loss, potentially attributable to the lack of a substantial magnetic field. On the other hand, Earth’s geodynamo appears to have been remarkably continuous since its inception, which probably occurred shortly after the Moon-forming impact. Therefore, magnetic shielding is a key factor that might significantly contribute to the discussion of whether a terrestrial-like planet will retain its water.This research investigated the dipolar magnetic moment of habitable planets in order to determine whether their magnetospheric protection is sufficient to shield the surface (and the potential liquid water on it) from the effects of X-EUV radiation, coronal mass ejections, cosmic rays, stellar winds and stellar magnetic fields. We show it is likely that only a small fraction of CHZ planets have a sufficient dynamo to sustain liquid water on their surfaces.  This result holds even if we assume a low threshold based on the magnetic dipole moment from Earth’s palaeomagnetic records.

Analysis of KOI 2700b: the second exoplanet with a comet-like dusty tail

Garai, Zoltán

Close-in exoplanets are subjected to the greatest star-planet interactions. This interaction may have various forms. In certain cases it may cause formation of a comet-like dusty tail. The Kepler object KOI 2700b was discovered recently as the second exoplanet with such a comet-like tail. It exhibits a distinctly asymmetric transit profile, likely indicative of the emission of dusty effluents and reminiscent of KIC 12557548b, the first exoplanet with a comet-like dusty tail. Our scientific goal is to verify the disintegrating-planet scenario of KOI 2700b by modeling its light curve and to put constraints on various tail and planet properties, as was done in the case of KIC 12557548b. We would like to understand better how the disintegration works at this uninhabitable planet, especially what is the typical particle size in the dusty tail, how big is the planet solid body and how fast is the mass loss from the planet. We obtained the phase-folded and binned transit light curve of KOI 2700b, which we subsequently iteratively modeled using the radiative-transfer code SHELLSPEC. We modeled the comet-like tail as part of a ring around the parent star and we also included the solid body of the planet in the model. During the modeling we applied selected species and dust particle sizes. We also analyzed the systematic evolution of the light curve and searched for possible long-term orbital period changes of KOI 2700b. We confirmed the disintegrating-planet scenario of KOI 2700b. Furthermore, via modeling, we derived some interesting features of KOI 2700b and its comet-like tail.

Methanol and carbon monoxide chemistry of protostellar envelopes

Perotti, Giulia

Carbon monoxide, CO, is a key molecule in the interstellar medium. It is the cornerstone for synthesizing complex molecules in the Universe, starting with methanol (CH3OH) and potentially leading to prebiotic molecules.  To model the solid and gas-phase CO and CH3OH abundances in star-forming regions, we developed a Simplified CO Network (SCON). SCON can either be coupled to a 1D physical model of collapsing protostellar envelopes or a sophisticated 3D MHD simulation of a collapsing molecular cloud. The advantage of this simplified network is that it allows us to run these models for the ~104 trace particles of the simulations. In the cold outer parts of the envelope, most of the gas is frozen out onto dust grains. As matter falls toward the star, the temperature increases and these molecules sublimate. In the 1D model, the collapse is radial and all CH3OH sublimates into the gas phase. In the 3D simulation, results show that only a small fraction of gas reaches a high enough temperature for CH3OH to sublimate. Hence, the total amount of gas-phase CH3OH is lower in the 3D model compared to the 1D model.  To benchmark the model predictions, we compare these to recently obtained observations of gas-phase CO and CH3OH from the SMA and APEX and ice CO and CH3OH from the VLT. Specifically, the data cover the envelope of the deeply embedded protostar Ser-SMM4 in the Serpens Main Cloud. The results of this benchmarking and the implications for the CO and CH3OH chemistry are presented. 

Primordial Mass and Density Segregation in a Young Molecular Cloud

Alfaro, Emilio J.

We analyse the geometry of the Pipe Nebula, drawn by the distribution (Q-spatial parameter) and hierarchy (spatial segregation) of column density peaks previously detected and catalogued. By analysing the mass and volume density of the cores, we determine that both variables shown to be spatially segregated and highly structured. Given the early evolutionary state of the Pipe Nebula, our results suggest that both, mass and volume density segregations, may be primordial, in the sense of appearing in the early phases of the chain of physical mechanisms which conform the star-formation process. We also propose that volume density, and not mass, is the pararameter that most clearly determines the initial spatial distribution of the pre-stellar cores.

The chemical fingerprint of Class I sources

Artur de la Villarmois, Eizabeth

The formation and evolution of protoplanetary disks are a fundamental ingredient in the process oflow mass star formation. In particular, Class I sources act as a ‘bridge’ between the deeplyembedded Class 0 sources and the emergence of protoplanetary disks, associated with Class IIsources. Thus, the study of Class I sources are of prime importance for our understanding of theformation and evolution of solar-type stars and their disks.In this work, we present an ALMA chemical survey of 10 Class I sources in Ophiuchus. Thecovered molecular transitions were chosen specifically to trace the kinematics of disk formation(i.e., C17O, H13CO+ and C34S) and the warm chemistry in the inner envelope or disk (i.e., SO2and CH3OH). The tracers reveal the chemistry and physics of the embedded disks, probing materialwith high temperatures and densities. In spite of a very high sensitivity, CH3OH is not detectedtoward any of these sources. This suggests that CH3OH gas only exists in a very thin layer betweenbeing frozen out as ice and photo-dissociated by UV radiation from the star. Furthermore, we findthat SO2 shows compact emission and the intensity correlates with the luminosity of the sources.Therefore, SO2 may be a better tracer of the warm gas and its associated chemistry in these sources.These observations show the existence of disk-like structures, associated with most of the sourcesof the sample, and highlight the differences in the physical structures between Class I sources andother stages of low-mass star formation.

Tracing the Transition from Atoms to Molecules in the ISM

Li, Di

The transition from atoms to molecules is a key step in star formation. The processes and results of this transition not only dominate the formation time scale of stars, but also could affect protostellar disk evolution. I report here new results based on two absorption techniques, namely, absorption against background quasars  (e.g. Heiles & Troland 2003) and HI narrow self-absorption (HINSA; Li & Goldsmith 2003).   Through analyzing HI/OH absorption and the corresponding CO emission, we revealed the OH excitation to follow an empirical log-normal distribution peaking around 3.4 K (Li et al. 2018). The closeness between the OH excitation temperature and the Galactic background (CMB+synchrotron) should explain the apparent weakness of OH emission, which was rarely mapped on larger scales nor found in other galaxies. As a simple hydride, however, OH is found to trace the total amount of H2 including the so-called dark molecular gas (DMG) in the intermediate extinction regime ( 0.2<av<2). oh="" has="" a="" tighter="" x-factor="" than="" co="" (xu="" &="" li="" 2016).  ="" based="" on="" the="" hinsa="" technique,="" we="" were="" able="" to="" identify="" an="" isolated="" dark="" cloud,="" b227,="" currently="" undergoing="" h2="" formation.based="" dust,="" co,="" nh3,="" and="" hi, ="" b227="" was="" shown="" have="" higher="" hi="" abundance="" in="" outside="" ring="" lower="" core.="" such="" gradient="" enabled="" us="" obtain="" limit="" of="" 5="" million="" years="" its formation="" time="" scale.="" core,="" [hi]="" [h2]="" measured="" be="" 0.1%,="" orders="" magnitude="" usually="" assumed="" chemistry="" models="" for="" protoplanetary="" disks="" (e.g. walsh="" et="" al.="" 2015). ="" absorption="" techniques="" thus="" provide="" crucial="" constraints="" formation="" molecules="" universe,="" affecting="" both="" cosmological="" simulations="" (e.g. gnedin="" 2009)="" star-formation="" models.="" further="" facilities,="" ska="" particular,="" could="" comprehensive="" information="" ism,="" terms="" total="" gas="" content="" including="" dmg="" excitation,="" through="" absorption ="" measurements="" (mcclure-griffith="" 2015).<="" p="">

CO destruction in proto-planetary disk midplanes

Bosman, Arthur

CO has long been thought to be the best mass tracer for proto-planetary disks as it can be easily detected with ALMA in many disks. However, the inferred gas masses from CO in recent ALMAobservations seem to be inconsistent with their inferred dust masses. Inferred gas-to-dust ratios orders of magnitude lower than the ISM value. Herschel measurements of HD imply gas masses in line with gas-to-dust ratios of 100. This suggests that at least one additional mechanism, next to freeze-out andphotodissociation, is removing CO from the gas-phase. We have tested the suggestion that the bulk of the CO is chemically processed and that the carbon is sequester in less volatile species such as, CO2, CH3OH and CH4 in the dense, shielded midplane regions of the disk.Using our gas-grain chemical code we did a parameter exploration and followed the the CO abundanceevolution over a range of conditions representative of disk mid-planes. The impact of the chemical parameters, tunnelling efficiency and diffusion was also studied. A reduction of the total CO abundance by a factor of 10-50 is found at high densities between 15 and 30 K on timescales of 3 Myr assuming an ionisation rate of 10-17 per second. Main reactions are identified. The order of magnitude destruction of CO is robust against the assumption on the chemical parameters between 20 and 30 K. Below 20 K there is a very strong dependence in the CO abundance on the efficiency of H tunnelling.The finding that CO is efficiently destroyed between 20 and 30 K on a 3 Myr timescale is encouraging since most of the 13CO and C18O emission is expected to come from parts of the disk with temperatures within this range.

Star formation efficiency in self-gravitating molecular cloud deviating from thermodynamic equilibrium

Kumssa, Gemechu

Abstract In this paper we present star formation efficiency  in free-fall time (SFE_{ff}) of self-gravitating molecular cloud which is deviating from thermodynamic equilibrium by a factor e where (0 < e < 1). Understanding efficiency of star formation in molecular cloud (MC) leads to know how, where and when of star formation in time. In this work we see the influence of  different parameters in triggering and controlling star formation efficiency in self-gravitating molecular cloud deviating from thermodynamic equilibrium. Based on the conceptual framework we have modeled equation of star formation efficiency (SFE_{ff}) in free fall-time for star forming MC under its own gravity and deviating from thermodynamic equilibrium. Its efficiency is relatively larger than that of star forming MC in thermod ynamic equilibrium. Fundamental parameters also varied in time and obtained that star formation efficiency of self-gravitating MC is affected by fundamental parameters present in modeled equation.Keywords  MC: self-gravitating MC; Star : Star Formation; thermodynamic equilibrium.

Dust dynamics and growth in young protostellar disks

Vorobyov, Eduard

I will report on the early evolution of dust in gravitationally unstable protostellar disks with different values of the viscous alpha-parameter and dust fragmentation velocity.  The disk evolution is studied using numerical hydrodynamics simulations modified to include a dust component consisting of two parts: sub-micron-sized dust and grown dust. The former is strictly coupled to the gas, while the latter interacts with the gas via friction and gravity. The conversion of small to grown dust, dust growth, settling, and dust self-gravity are also considered.I will show that the process of dust growth known for the older protoplanetary phase also holds for the embedded phase of disk evolution. The process of small-to-grown dust conversion is very fast once the disk is formed. The total mass of grown dust in the disk reaches hundreds of Earth masses already in the embedded phase of star formation, and even a greater amount of grown dust drifts in the inner, unresolved 1 AU of the disk. Nevertheless, the bulk of the disk is usually dominated by small dust, except for the inner several tens of AU where grown dust prevails, thanks to efficient inward radial drift of grown dust and continuing replenishment by small dust from the infalling envelope. Dust does not usually grow to radii greater than a few cm, with a notable exception of models with alpha <= 10-3, in which case a zone with reduced mass transport develops in the inner disk and dust can grow to meter-sized boulders in the inner 10 AU. The efficiency of grown dust accumulation in spiral arms is stronger near corotation where the azimuthal velocity of dust grains is closest to the local velocity of the spiral pattern. The implications of fast dust growth for planet formation will also be discussed.

Exploring DCO+ as a tracer of dust evolution in planet-forming disks

Salinas, Vachail

In planet-forming disks, deuterated species like DCO+ often show up in rings. Two chemical formation routes contribute: cold deuteration at temperatures below 30 K and warm deuteration at temperatures up to 80 K. In this work we reproduce the DCO+ emission in the disk around HD163296 using a simple 2D chemical model for the formation of DCO+ through the cold deuteration channel and a parametric treatment of the warm deuteration channel. We use data from ALMA in band 6 to obtain a resolved spectral imaging data cube of the DCO+ J=3–2 line in HD163296 with a synthesized beam of 0."53× 0." 42. The observed DCO+ emission is reproduced by a model with cold deuteration producing abundances up to 1.6e-11. Warm deuteration, at a constant abundance of 3.2e-12, becomes fully effective below 32 K and tapers off at higher temperatures, reproducing the lack of DCO+ inside 90AU. Throughout the DCO+ emitting zone a CO abundance of 2e10-7 is found, with ~99% of it frozen out below 19 K. At radii where both cold and warm deuteration are active, warm deuteration contributes up to 20% of DCO+, consistent with detailed chemical models. The decrease of DCO+ at large radii is attributed to a temperature inversion at 250 AU, which raises temperatures above values where cold deuteration operates. This return of the DCO+ layer to the midplane reproduces the local DCO+ emission maximum at ~260AU. We can use the morphology of DCO+ emission to trace the temperature substructures of disks produced by dust evolution processes. Outer disk temperature inversions, expected when grains decouple from the gas and drift inward, can lead to secondary maxima in DCO+ emission and a reduction of its radial extent. This can appear as an outer emission ‘ring’, and can be used to identify a second CO desorption front.

Low mass star formation in quiet and violent environments

Toth, L. Viktor

The formation of Solar System might happened in a violent environment. On the other hand solar mass stars may also form without external trigger. Recently Galactic cold clumps (PGCC) were located based on Planck all sky mapping data. Our radio spectral line observations uncovered the distribution and physical properties of cold interstellar medium in dozens of PGCCs. These are faced to all kinds of external effects being embedded into various environments. Heiles cloud 1 also known as L1251, and Heiles cloud 2 bearing TMC-1 will be shown as two examples of low mass star forming clouds in different environments.

Knotty protostellar jets as a signature of episodic protostellar accretion?

Vorobyov, Eduard

The possible causal link between the knotty jet structure in CARMA 7, a young Class 0 protostar in the Serpens South cluster, and episodic accretion in young protostellar disks will be demonstrated. The protostellar accretion history was derived using numerical hydrodynamics simulations of gravitationally unstable disks around solar-mass protostars showing luminosity bursts caused by dense gaseous clumps spiraling on the protostar (Vorobyov & Basu 2015, ApJ).  I will show that the time spacings between the luminosity bursts correlate with the time spacings between the knots in the jet of CARMA 7, if a certain correction for the (yet unknown) inclination angle with respect to the line of sight is applied to the observational data. Implications of episodic accretion for dust growth, chemical disk composition, stellar evolution, and planet formation will be discussed.

Anthropic Principle and the Hubble Constant

Krizek, Michal

The so-called weak formulation of the Anthropic Principle states that all fundamental physical constants have just such values that they enabled the origin of life. We show that also the Hubble constant significantly contributed to the existence of mankind [1]. Life on Earth has existed continually for at least 3.5 Gyr and this requires relatively stable conditions during this very long time period. However, since the luminosity of the Sun increases, the Earth should recede from the Sun. We present several examples indicating that the Solar System expands by a speed comparable to the Hubble constant. This guarantees that the Earth received almost constant solar flux during the last 3.5 Gyr.   We give three independent arguments showing that the average Earth-Sun distance increases about 5 m/yr due to the finite speed of gravitational interaction. Such a large recession speed cannot be explained by solar wind, tidal forces, plasma outbursts from the Sun, or by the decrease of the Solar mass due to nuclear reactions. Models based on Newtonian mechanics can explain only a few cm per year.   The measured average increase in the Earth-Moon distance is 3.84 cm/yr, while Newtonian mechanics is able to explain only 2.1 cm/yr. We claim that this difference is also caused by the finite speed of gravitational interaction and its size is comparable with the Hubble constant. Mars was much closer to the Sun as well, otherwise it could not have had rivers 3.5 Gyr ago, when the Sun’s luminosity was only 75 % of its present value [2].References[1] M. Krížek, Dark energy and the anthropic principle, New Astronomy 17 (2012), 1–7.[2] M. Krížek, L. Somer, Manifestations of dark energy in the Solar system, Grav. Cosmol. 21 (2015), 58–71.

Finding flares in Kepler data using machine learning tools

Vida, Krisztián

Long photometric surveys, like the Kepler database is a gold mine for studying flares. However, identifying them is a complex task: while in the case of single-target ground observations it can be easily done manually by visual inspection, this is nearly impossible for year-long time series for several thousand targets. Although there exist automated methods for this problem, several problems are difficult (or impossible) to overcome with traditional fitting and analysis approaches. In this poster we introduce a method for identifying flares based on machine learning methods, which are intrinsically adept in handling such data sets.

Stellar coronal mass ejections and their possible effects on habitability

Vida, Krisztián

Flares and coronal mass ejections (CMEs) are the most prominent, most energetic events of stellar activity. These events can have high importance in exoplanet studies they can erode or irreversibly alter the atmospheres of orbiting planets, rendering them uninhabitable. On the Sun, CMEs are studied in high detail, both by observation and modeling, and they are seen rather frequently: 0.5-6 CME/day. On other stars, however, there are only a handful of CMEs observed up to now. We present an extensive search of observational archives - the virtual observatory - in the hope of finding the missing events, and consider how these eruptions could influence the circumstellar planets and their habitability.

Transfer and loss of water in hit-and-run collisions during late-stage planet formation

Burger, Christoph

Collision events between large, similar-sized bodies shape the final characteristics of (terrestrial) planets. Volatile material like water is particularly prone to collisional loss processes, due to its volatile nature, but also because it is preferentially found in the outer layers of colliding bodies. We studied transfer, loss and processing of water in collisions between planetary embryos in the late stages of planet formation, focusing on the peculiarities of hit-and-run collisions. This additional outcome regime emerges in rather grazing encounters between roughly similar-sized bodies and is characterized by two large post-collision objects, originating mainly from the two pre-collision bodies respectively. Besides the common figure of overall water loss, transfer between the two colliding bodies as well as their individual losses have to be considered in hit-and-run encounters._x000D_ For disentangling these effects we ran a suite of multi-material Smooth Particle Hydrodynamics (SPH) simulations including self-gravity, with varying impact velocity, impact angle and projectile-to-target mass ratio over the full range of reasonable values. We find overall water losses of up to 75% in the most energetic impacts, and much greater effects for the smaller body, which is often stripped of a large fraction of its volatiles while the larger body remains relatively unaltered. Therefore the cumulative effect of a sequence of such collisions can be expected to greatly reduce water contents of growing planets._x000D_ To additionally study the amount of water vapor production in connection to potential further losses of water vapor atmosphere, we also varied the total colliding mass. Results indicate that these additional losses are particularly important in collisions of ~Mars-sized embryos, where vapor production is already significant, but their gravity to prevent atmospheric losses is still weak.

Retention of Small Charged Dust in Planet Forming Disks

Akimkin, Vitaly

Dust evolution in disks around young stars is a key ingredient to the global disk evolution and accompanying planet formation. The mutual sticking of initially small grains is not straightforward and may be hampered by several processes. This includes dust grain bouncing, fragmentation, electrostatic repulsion and fast drift to the central star. In this study we aim at theoretical modeling of the dust coagulation coupled with the dust charging and disk ionization calculations. We show that the electrostatic barrier is a strong restraining factor to the dust coagulation in the micrometer size regime. While the sustained turbulence helps to overcome the electrostatic barrier, dust fluffiness limits its potential. Coulomb repulsion may keep a significant fraction of dust at 1-10um size range in vast regions of protoplanetary disks.

S-type planets formation in close binaries: scattering induced tidal capture of circumbinary planets

JI, Jianghui

Although several S-type and P-type planets in binary systems were discovered in past years, S-type planets have not yet been found in close binaries with a separation not more than 5 au. Recent studies suggest that S-type planets in close binaries may be detected using the current high-accuracy radial velocity (RV) and photometric measurements. However, current planet formation theories generally suggest that it is difficult for S-type planets in close binaries systems to form in situ. In this study, we extensively perform numerical simulations to explore the scenarios of planet-planet scattering among circumbinary planets and subsequent tidal capture in various binary configurations, to examine whether the mechanism can play a part in producing such kind of planets. The maximum capture probability is approximately %10, which can be comparable to the tidal capture probability of hot Jupiters in single star systems. The capture probability is related to the binary configuration, where a smaller eccentricity or a low mass ratio of the binary will lead to a larger probability of capture, and vice versa. Furthermore, we find that the S-type planets with retrograde orbits can be naturally produced during capture process. These planets on retrograte orbits can help us distinguish in situ formation and post-capture origin of S-type planet in close binaries systems. The forthcoming missions such as PLATO will provide the opportunity and feasibility to detect these planets. Our work provides several suggestions for selecting target binaries to search S-type planets in the near future according to the investigation.

Chemical Evolution and the formation of Planets on the primordial Universe

Corazza, Lia

We present a discussion about the relation between planet formation on the primordial universe and the cosmic chemical evolution. We developed a semi-analytical model that provides the evolution for 11 chemical elements since Pop III stars (Z = 0) started to die until the formation of Pop II stars with metalicity Z = 2.10-2 Zsolar . Results indicate that C, N and O could play a very important role on the formation of planets. By modelling the cosmic planet formation rate (earth-like and gas giants) estimated in [1] and the amount of metals removed from the interstellar medium in the formation process, we can investigate the role of chemical elements (mainly C, N and O) on the formation of planets since the universe was very young (about 180 Myr, z = 20). We are also able to briefly dicuss at what point the avaibility of metals in the universe could provide conditions to foster the formation of the first chemical building relevant to the appearance of life.[1] Zackrisson, E., Calissendorff, P., Gonzalez, J., Benson, A., Johansen, A., Janson, M. Terrestrial Planets across Space and Time. ApJ, 833. 2016.

Computing Models of M-type Host Stars and their Panchromatic Output

Linsky, Jeffrey

We have begun a program of computing state-of-the-art model atmospheres from the photospheres to the coronae of M stars that are the host stars of known exoplanets. For each model we are computing the emergent radiation at all wavelengths that are critical for assessing photochemistry and mass-loss from exoplanet atmospheres. In particular, we are computing the stellar extreme ultraviolet radiation that drives hydrodynamic mass loss from exoplanet atmospheres and is essential for determining whether an exoplanet is habitable. The model atmospheres are computed with the SSRPM radiative transfer/statistical equilibrium code developed by Dr. Juan Fontenla. The code solves for the non-LTE statistical equilibrium populations of 18,538 levels of 52 atomic and ion species and computes the radiation from all species (435,986 spectral lines) and about 20,000,000 spectral lines of 20 diatomic species. The first model computed in this program was for the modestly active M1.5 V star GJ 832 by Fontenla et al. (ApJ 830, 152 (2016)). We will_x000D_ report on a model for the more active M5 V star GJ 876 and compare this model and its emergent spectrum with GJ 832. In the future, we will compute and intercompare semi-empirical models and spectra for all of the stars observed with the HST MUSCLES Treasury Survey, the Mega-MUSCLES Treasury Survey, and additional stars including Proxima Cen and Trappist-1. This talk is dedicated to the memory of Dr. Juan Fontenla who passed away in January 2018. This multiyear theory program is supported by a grant from the Space Telescope Science Institute.

Exo-environment in solar neighborhood: from molecular gas to protoplanet disks

Hojaev, Alisher S.

Relying on the data of complex general catalog we compiled using the KDD method (knowledge discovery in databases), the 3-D distribution and physical properties of molecular clouds in local galactic environments of the Sun were analyzed. We also combined a detailed database of the star formation indicators and young-star populations in the solar neighborhood, and protoplanetary accretion disk evidences around CTTS and WTTS were considered and discussed. The search and detailed study of exoplanets and protoplanets on 4 meter fully adaptive telescope with laser-guide-star technology which is creating to install at Maidanak astrophysical observatory (Uzbekistan) having the perfect seeing conditions as well as an appropriate geographical localization to support the time-series observations as well as other time domain astronomy features are included into scientific program of the telescope and discussed in report.

Observations of H2O and OH masers in star-forming regions

Rudnitskij, Georgij

We report long-term observations of H2O and OH maser emission sources at wavelengths of 1.35 and 18 cm associated with star-forming regions. The observations were carried out, respectively, on the 22-metre radio telescope of the Pushchino Radio Astronomy Observatory, Russia, and on the radio telescope of the Nançay Radio Astronomy Station, France._x000D_ The sample includes about 150 sources. Some of them are well-known masers, such as Ori A, W43M3, W51, W75N. Strong quasi-periodic flares of maser emission have been observed. We invoke, where available, interferometric data on the sources and trace the fate of individual maser features, the variations of their flux densities and radial velocities. In particular, the velocity drift of some features on a timescale of several years was observed. Several sources (in particular, G25.65+1.05, IRAS 16293-2422, Cep A) have displayed strong flares in the H2O line, when their peak flux desnity raised by a few orders of magnitude above the quiet state. Possible causes of this are discussed, among them consecutive excitation of the maser by a propagating shock wave and processes related to turbulence and graviatational instability in the circumstellar protoplanetary discs._x000D_ Other sources are new, recently discovered, strong emitters in the H2O and OH lines associated with quite young star-forming regions traced by Class I methanol masers radiating in the 44 GHz 70-61A+ transition of CH3OH.We attempt to range the sources observed according to the presence or absence of this or that maser (CH3OH, H2O, OH), thus creating an evolutionary sequence of the star-forming regions hosting these masers.

ALMA observations of oxygen-bearing complex organic molecules towards the low-mass protostellar binary IRAS 16293--2422

Manigand, Sébastien

Many questions remain concerning the formation of complex organic molecules and their presence in the inner region of solar-type protostars. The nearby low-mass Class 0 protostellar binary IRAS 16293--2422 (IRAS16293 hereafter) is an excellent object to study these species on solar system scales. The Atacama Large Millimeter/submillimeter Array (ALMA) provides the high angular and spectral resolution as well as the sensitivity needed to study the physical and chemical structure of such protostars in unprecedented detail._x000D_ We use observations from the Protostellar Interferometric Line Survey (PILS; Jørgensen et al. 2016), an unbiased line survey of IRAS16293 using ALMA, to analyse oxygen-bearing complex organic molecules in both IRAS16293A and IRAS16293B. A comparative analysis of the two sources reveals differences in abundances for some of the species and their isotopologues. For example, formaldehyde (H2CO), glycolaldehyde (CH2OHCHO) and ethylene glycol (CH2OH)2 are more than one order of magnitude more abundant towards the A source compared to the B source measured relative to methanol._x000D_ In contrast, methyl formate (CH3OCHO), ethanol (C2H5OH) and dimethyl ether (CH3OCH3) show similar abundances towards the two components. In addition, the high sensitivity of the ALMA observations enabled many deuterated species to be detected, including doubly-deuterated methyl formate (CHD2OCHO) for the first time in the ISM (Manigand et al. 2018,subm.). The D/H ratio of CHD2OCHO and CH2DOCHO were found to be extremely enhanced compared to the canonical value 2 x 10-5, with CHD2OCHO D/H ratio 2--3 times higher than CH2DOCHO D/H ratio. Abundance and D/H ratios suggest that methyl formate forms through grain surface reactions involving H2CO and CH3OH photodissociation products (Chuang et al. 2016) and the deuteration enhancement is driven by H-D abstraction substitution processes on the grain.

Origin of Spin-Orbit Misalignments and Formation of Close-in Giant Planets

Lai, Dong

The origins of hot Jupiters (HJs, with periods < 10 days) and warm Jupiters (WJs, with periods 10-200 days) remain an outstanding problem in exoplanetary astrophysics. Possible formation channels range from high-eccentricity migration induced by planet-planet or planet-binary interactions to disk-driven migration or even in-situ formation. A significant fraction of these close-in giant planets have been found to have misaligned planetary orbital angular momentum axis relative to the spin axis of the host star. How are spin-orbit misalignments produced? We will discuss/review our recent works on the production of spin-orbit misalignments in different HJ/WJ formation channels. Topics include: (1) The role of chaotic stellar spin dynamics as the giant planet undergoes high-eccentricty migration; such stellar spin variation/dynamics plays a dominant role in determining the final spin-orbit misalignment; (2) The possibility of producing primordial spin-orbit misalignment in the disk migration scenario as a result of star-planet-disk-binary interactions; (3) The possibility of producing misaligned multi-planetary systems; (4) The presence or lack of spin-orbit misalignment in a planetary system as a probe of the planet's dynamical history and the physical processes taking place in the planet's birth environment (protoplanetary disks, binaries, etc).

Chemical signatures of FU Ori outbursts

Molyarova, Tamara

FU Ori type young stellar objects are known to experience sudden outbursts, their luminosity growing by 1-2 orders of magnitude. These objects are typically observed in their outburst state, which lasts for several decades, but are difficult to find in the quiescent state. The tool to identify the object that has passed through the luminosity outburst some time ago might be provided by disk chemistry. The disk heating and the enhanced radiation field during the outburst affect dramatically the disk chemical composition, evaporating abundant ices and accelerating chemical reactions. Some of the outburst chemical consequences may stay noticeable long enough to identify them after the outburst, when the luminosity is back to normal. We perform astrochemical modeling of protoplanetary disks before, during and after an FU Ori outburst. We find species that are especially sensitive to the luminosity growth, as well as those able to retain signatures of the outburst after it has finished. We probe the impact of disk parameters and dust size on the chemical composition of the selected species.

The impact of flares and CMEs on planetary atmospheres

Guenther, Eike

Recent studies have shown that planets in the mass-range between 2 and 400 MEarth have a huge spread in densities. Even planets of the same mass can have very different densities. How can this diversity be explained? In the first 100 million years of their evolution, planets are exposed to strong EUV and X-ray (XUV) radiation from the host star. Observations, and theoretical models have shown that such radiation can lead to the erosion of planetary atmospheres. This process naturally explains the diversity of planets: Planets with atmospheres have low densities, planets without atmospheres have high densities. If this idea of atmospheric erosion were correct, it would have important consequences for the habitability of planets, since planets without atmospheres cannot be habitable. The erosion of planetary atmospheres is particularly important for potentially habitable planets of M-stars, because they orbit at very short distances from the host stars were the erosion is particularly strong. In recent years it became clear that the quiescent XUV-radiation is usually not strong enough to erode the atmospheres of planets completely. However, very little is known about the impact of flares and coronal-mass ejections (CMEs) on planetary atmospheres within the first 100 million years of their evolution. The situation is particularly difficult for CMEs, as only very few such events in young M-stars have been observed. Thanks to the new instrumentation, it is now possible to determine the flare-rate for young M-stars, and to study also the CMEs. Using data obtained with the Kepler satellite, we determine the statistics of flares of more than 100 M-stars with an age of 17 Myrs, and determine the power-law index of the flare-distribution. We also obtained more than 1000 high-resolution spectra of active M-star to study the properties of CMEs, and compare them with CMEs observed on the Sun. 

Possibility to locate the position of the H2O snowline in protoplanetary disks through spectroscopic observations

Notsu, Shota

Observationally locating the position of the H2O snowline (e.g., Hayashi et al. 1981, 1985) in protoplanetary disks is crucial for understanding the planetesimal and planet formation processes, and the origin of water on the Earth. The velocity profiles of emission lines from disks are usually affected by Doppler shift due to Keplerian rotation. Therefore, the line profiles are sensitive to the radial distribution of the line emitting regions. In our previous works (e.g., Notsu et al. 2016&2017, ApJ), we calculated the chemical composition of the disks around a T Tauri star and a Herbig Ae star using chemical kinetics, and then the ortho-H216O line profiles to identify that lines with small Einstein A coefficients and relatively high upper state energies (~1000K) are dominated by emission from the hot midplane region inside the H2O snowline, and therefore through analyzing their profiles the position of the H2O snowline can be located. In addition, we analyzed the ortho- and para-H218O molecular lines to find that they trace deeper into the disk than the ortho-H216O lines since the number density of H218O is low (Notsu et al. 2018a, ApJ). Thus these H218O lines are potentially better probes of the position of the H2O snowline at the disk midplane, depending on the dust optical depth. Since the values of the Einstein A coefficients of sub-millimeter candidate water lines are low, H218O and para-H216O lines with relatively lower upper state energies (~ a few 100K) can also locate the position of the H2O snowline. There are several candidate water lines that trace the position of the H2O snowline in ALMA Bands 5-10. Finally, we have proposed the water line observations for a Herbig Ae disk HD163296 in ALMA Cycle 3, and partial data were delivered. We constrain the line emitting region (the location of the H2O snowline) and the dust properties from the observations.

Direct infall signatures and complex organic molecules toward an isolated embedded protostar BHR71

Yang, Yao-Lun

Star formation processes such as infall, accretion, and outflows increase the complexity of molecules, allowing us to use those molecules to probe the physical environments where stars form.  The most deeply embedded protostars present particularly rich spectra of molecules due to their dense envelope and active infall and outflows, making them best probed by molecular spectroscopy.  Stars form via the infall of mass from a core, but direct evidence for such infall has been elusive.  The most direct probe of infall is redshifted absorption against the central continuum source, which is best shown in dense gas tracers, such as HCO+ and HCN.  Our ALMA observations of these two molecules show such redshifted absorption toward an isolated core, BHR71.  Both lines show a similar redshifted absorption profile, but the HCN line has a wider (9 km/s compared to 5 km/s) line width, suggesting that it traces faster infalling gas closer to the central protostar.  We model the line profiles with 1D and 3D radiative transfer calculations to further constrain the physical properties of the collapsing envelope.  We also found emissions of complex organic molecules around 345 GHz.  BHR71 shows a similar suite of lines compared to another isolated core, B335, which only has 10% of the luminosity of BHR71 but is at a similar evolutionary stage.  We found that complex organic molecules emit from a compact region centered on the continuum source, which is barely resolved with a beam of 0.27", corresponding to ~50 AU.  We identify the origins of this emission and constrain the excitation environment to compare with current paradigms of the structure of inner envelope and disks.  We investigate the physical environment in the inner 50 AU via emission of complex organic molecules; combined with the redshifted absorption we can follow material from the envelope to the central protostar.

Pebble accretion onto planets in turbulent discs

Kley, Wilhelm

Planets are born in protoplanetary discs growing from very small particles to full-grown planets.In the past years, it has been recognized that the growth process can be sped-up by accreting alarge number of solid, pebble-sized objects that are still present in the protoplanetary disc.It is still an open question how efficient this process is in realistic turbulent discs.In this contribution we present results on the accretion efficiency of pebbles in turbulent discsthat are driven by the purely hydrodynamical vertical shear instability (VSI).We perform global three-dimensional simulations of discs with embedded planets of different massesranging from 5 to 100 Earth masses. Embedded in the flow is a swarm of pebbles in ten size binsthat move under the action of drag forces between gas and particles.For well-coupled particles with unity Stokes number we find an accretion efficiency(rate of particles accreted over particles drifting inward) of about 2% for the lower massplanets. For masses between 10 and 30 Earth masses the core reaches the pebble isolation massand the particles are trapped at the pressure maximum just outside of the planet,shutting off further particle accretion.

Impact of the interstellar medium on processes on Earth

Bochkarev, Nikolai

Impact of the interstellar medium on processes on EarthN.G.Bochkarev Sternberg Astronomical Institute of Moscow State University The paper discusses possible impacts of the interstellar matter (ISM) on processes on Earth, first of all those, which may affect the Earth biosphere. ISM parameters, determining the degree of penetration of galactic cosmic rays, interstellar atoms and ions into the Solar system and their impact on Earth varies considerably as the Sun moves through different ISM regions. In some cases the impact may provoke severe environment changes substantial for the life on Earth.

Towards the search of the difference in physical and dynamical properties between the L4 and L5 swarms of Jupiter Trojans

Slyusarev, Ivan

From the beginning of the study of Jupiter Trojans, there is a well-known difference in number of objects between L4 and L5 groups. For a long time, this difference has been attributed to the observational selection effect. However, as the number of discovered Trojans increase, L4 Trojans the difference become even more noticeable. At present, there are 4599 objects known in L4 and 2433 in L5 population, i.e. L4 Trojans are more numerous than L5 in 1.9 times. We found that the shape of the orbital inclinations distribution in the L4 and L5 swarms are also different (Slyusarev 2013). The L5 population shows significantly wider distribution with a plateau in the range from 5° to 17° and a weak maximum at 27°. The distribution of the L4 population demonstrates a sharp maximum at 7°, after which the number of Trojans with specified inclinations decreases exponentially. These two manifestations of asymmetry in the L4 and L5 swarms weren't explaned yet. The asymmetry of L4 and L5 swarms is difficult to explain basing on dynamical models. We search for possible differences in physical parameters between Trojans belonging to the L4 swarm and to that belonging to L5 swarm using our own observations and literature data.

Observed versus modelled stellar CME rates

Leitzinger, Martin

Stellar coronal mass ejections (CMEs) may play an important role in stellar and planetary evolution, therefore the knowledge on parameter distributions of this energetic activity phenomenon is highly relevant. During the last years several attempts have been made to detect stellar CMEs of late-type main-sequence and pre main-sequence stars from dedicated optical spectroscopic observations. Up to now only a handful of distinct stellar CME detections are known which contradicts the results from stellar CME modelling, which predict higher CME rates. We report on dedicated ongoing and future observational attempts to detect stellar CMEs and discuss the observational results with respect to the results from stellar CME modelling. 

How many suns are in the sky? - Multiplicity surveys of exoplanet host stars

Mugrauer, Markus

In order to determine the true impact of stellar multiplicity on the formation and on the evolution of planets, we have initiated direct imaging surveys to search for (sub)stellar companions of exoplanet host stars on close orbits, as their gravitational impact on the planet bearing disk at first and on formed planets afterwards is expected to be maximal. According to theory these are the most challenging environments for planet formation and evolution but might occur quite frequently in the milky way, due to the large number of multiple star systems, which reside within in our galaxy. Here we will show some results, obtained so far in the course of our AO and Lucky-imaging campaigns of exoplanet host stars, conducted with NACO at the Paranal observatory in Chile for southern and with AstraLux at the Calar Alto Observatory in Spain for northern targets, respectively. In addition, we will introduce our new high contrast imaging project of southern exoplanet host stars, recently started with SPHERE, the new high contrast AO imager operated at the ESO-VLT, and we will present some first results of this survey.

Multiplicity study of T Tauri stars in the Lupus star forming region

Mugrauer, Markus

We have carried out a high contrast imaging survey for stellar and substellar companions among young pre-main sequence stars in the Lupus star forming region. For this long-term project we have utilized the adaptive optics imager NACO of the ESO-VLT, operated at the Paranal observatory in Chile. Here, we will present the results of this survey. In several observing campaigns we could obtain diffraction limited deep IR imaging data and have detected faint co-moving companions around our targets, whose astrometry (angular separations and position angles) as well as IR photometry was determined in all observing epochs. The co-moving companions found in our survey exhibit angular separations in the range between about 0.1 up to a few arcsecs, which corresponds to projected separations between about 10 up to a few hundreds of au, at the distances of our targets (about 140pc, in average). Beside several new binary and triple star systems, whose multiplicity was revealed in this survey, also faint co-moving companions in the substellar mass regime could be identified close to some of our targets.

Synthetic Observations of A Young Forming Circumstellar Disk

Tomida, Kengo

Angular momentum transport is one of the key processes in star and circumstellar disk formation. While many physical processes such magnetic braking, outflows and gravitational torque via asymmetric structures can contribute to angular momentum transport, their relative importance must be constrained by observations. Also, since observations of young circumstellar disks are developing rapidly especially with ALMA, realistic theoretical models that can be directly compared with observations are highly demanded. Synthetic observations with post-processing radiation transfer calculations allow us to derive physical quantities such as spectral energy distribution and intensity distribution from hydrodynamic simulations. We perform a long-term resistive MHD simulation of star and circumstellar disk formation. The formed circumstellar disk is initially small but grows as accretion continues. A pair of spiral arms are formed due to gravitational instablity, and they transform angular momentum efficiently. These spiral arms disappear by winding on a short dynamical time scale, but they form recurrently as gas accretion makes the disk unstable again. We perform synthetic observations and compare our results with the ALMA observation of Elias 2-27 (Perez et al. 2016), whose circumstellar disk has a pair of grand-design spiral arms. We find that the spiral arms are in good agreement with material spiral arms formed by gravitational instability. It is important to consider such a massive disk as the initial and boundary conditions for planet formation.

Triggered Formation of Star Clusters

Palous, Jan

Gould's belt with its star forming regions and OB associations, and the galactic supershell GS242-03+37 with associated young stars clusters, serve as examples of the triggered star formation due to the gas density increase in walls of expanding shells. We shall discuss how frequently similar events may happen in the differentially rotating disks of spiral galaxies and what role the supernovae play in this scenario. Interior volume of the expanding shell contains the interstellar medium enriched with the yields of the evolution of the parent stars. This medium mixes with the gas collected in the shell walls where the new clusters form.

Constrain the atmospheric properties of Wasp-31b using models.

Chouqar, JamilaBenkhaldoun, Zouhair

Wasp-31b, is a planet of 0.48 Jupiter masses and 1.55 Jupiter radii, with orbital period of 3.4-day around a metal-poor, late-F-type, V = 11.7 dwarf star. This gives it a large atmospheric scale height that makes it a good target for transmission spectroscopy._x000D_ Previous works studied the presence of Potassium in this exoplanet. Sing et al (2014) present an optical and near-IR transmission spectra of the atmosphere of WASP-31b obtained with the HST and show the presence of a strong potassium line. In contrast Gibson et al (2017) reports a spectrum of the atmosphere of WASP-31b, obtained with the FORS2 instrument on the VLT and find that there is no strong potassium line. Here, we take the publish data of WASP-31b (the datasets from Sing and Gibson's papers) and using models, we try to find a case where both solutions are correct by considering different cloud scenarios.

Chemical evolution of water in the protostellar environment

Jensen, Sigurd

Understanding the evolution of water during star formation, from the molecular cloud down to the circumstellar disk, is a central goal of astrochemistry.Open questions on this topic are how the water content is influenced by the local environment in which the protostar is formed, whether water is inherited directly from the molecular cloud and what role local processing during the cloud collapse plays for the water in the protoplanetary disk.We focus on the deuteration of water (HDO/H2O and D2O/HDO) as a tracer for the physical and chemical evolution of water around young protostars.We investigate the effects of the inhomogeneous star formation process by studying the formation of several hundred protostars in a realistic 3D MHD simulation of a molecular cloud from pc to tens of AU scales.For each of these protostars, we have large number of tracer particles available which track the gas flow providing the physical evolution of the material. On these particles, we evolve the chemical network from pre-collapse conditions down to the scales of the protostellar disk in a 3-phase model which includes both gas, surface and mantle species and track the buildup of ices species layer by layer.The theoretical results will be combined with incoming high-resolution ALMA observations of water and its isotopologues around young protostars. With the combination of an increased observational and theoretical sample we aim to pinpoint the important steps in the evolution of water and constrain the origin of water in the Solar System.

Submission for 'Planets Days' Juno mission and supporting observations from the GEMINI telescope

Kedziora-Chudczer, Lucyna

The Juno spacecraft is placed in the 53-day orbit around Jupiter taking data of its atmospheric composition, magnetic fields and gravity that will help to answer many fundamental questions about planetary formation, evolution and physics. I will discuss the most detailed maps of Jovian clouds and radiometric measurements that probe planetary weather systems to unprecedented depths. I will focus on Juno’s observations of Jovian auroras that are formed in high-latitude atmospheric layers as a result of charged particles precipitating from planetary magnetosphere. Juno’s study of the Jovian polar regions is complemented by observations from the ground telescopes. Our observations of Jupiter aurora with the GNIRS spectrograph at the Gemini telescope provide high-resolution (R~18000), near-infrared H3+ auroral emission maps in the planetary polar regions. These can be used to estimate temperatures and ion density profiles in the upper ionosphere of Jupiter. Juno's measurements of particle energies in the planetary magnetosphere combined with information from the infrared emissions, will help us to understand how the ionosphere of the planet responds to heating. 

Search for water on extrasolar planets with polarimetric observations

Kedziora-Chudczer, Lucyna

Light scattered from the atmosphere of a planet and its surface is polarised. In contrast, light from solar-type stars is largely unpolarised. Therefore polarimetry can be used for the detection and characterisation of extrasolar planets around such stars. The degree of polarisation due to reflected starlight depends strongly on the composition and physical properties of planetary atmospheres. Ultimately observations of polarisation could provide the clues about the water droplets in the planetary atmosphere and possible detection of liquid water on the planetary surface via glint reflection.I will discuss polarimetric observations of hot Jupiters with the high precision polarimeter, HIPPI at the Anglo Australian telescope built at the UNSW. I will also describe capabilities of the newly developed polarimeter, HIPPI-2, to be used on the 8-metre Gemini telescope.

Volatile Links between IRAS16293-2422B and 67P/C-G

Drozdovskaya, Maria

Comet 67P/Churyumov-Gerasimenko has been studied with in situ measurements by various instruments (ROSINA, COSAC, VIRTIS, MIRO) aboard the Rosetta spacecraft, which show that the comet has a rich molecular inventory and that there are complex relationships between various species. These data are one of the best probes of the innate protosolar disk that evolved into our modern day Solar System. Similar chemical richness, including large complex organic species, extends beyond the Earth and our Solar System as attested by countless observations towards high- and some low-mass protostars. One of the best-studied low-mass systems is IRAS16293-2422, which is thought to be analogous to the earlier phases of our Solar System. The region has been surveyed with the large unbiased ALMA Protostellar Interferometric Line Survey (PILS), which allowed its study with an unprecedentedly wide spectral range at high spectral and spatial resolutions. Thereby, its full chemical inventory and the spatial distribution of the detected species could be uncovered. This ALMA data on IRAS16293-2422 can be used to probe the extrasolar chemical content and the Rosetta measurements of 67P/C-G as a Solar System diagnostic. By deriving relative ratios for simple and complex organic molecules, direct comparisons can be drawn between the two to go after the origins of the chemical content of our Solar System. In this talk, results of such a comparative study will be presented, based on relative ratios of major and minor volatile species to access the degree of relative complexity stemming from common parent species. These results give clues to the different radicals available in the ices for subsequent synthesis of larger molecules, shedding light on the dominant pathways to chemical complexity and the physical conditions that optimize such enrichment. The carried out comparative work between protostars and 67P/C-G gives hints on the uniqueness of the ingredients to life.

Global Protoplanetary Disk Simulations: Dead Zone Formation and FUor Outbursts

Kadam, Kundan

The formation of low mass stars through protoplanetary disks is a highly complex process which involves time-dependent accretion. This is evident in variable young stars called FUors which show sudden brightening by a factor of about 100, lasting for several decades. We investigate one particular physical mechanism behind such FUor outbursts, the gravo-magneto instability. I will present the results of 2D global hydrodynamic simulations of protoplanetary disk evolution, starting with the collapse phase of the molecular cloud. We use a layered disk prescription with an adaptive Shakura-Sunyaev $\alpha$. With canonical values of the layered disk parameters, self-consistent dead zones form in the region between 1-4 AU, which are characterized by high surface density rings and a low effective viscosity. The continual accretion of material at the dead zone eventually triggers the gravo-magneto instability, giving rise to outbursts similar to those observed in FUors. I will also discuss the implications of our simulations on planet formation, and observability of the dead zone features through high resolution sub-millimeter and infrared techniques.

Observational evidence that asteroids formed big

Dermott, Stanley

A century ago Hirayama discovered the clustering of asteroid orbital elements, revealing that some asteroids are in families originating from the disruption of a few large primordial bodies. However, the asteroids now classified as family members constitute a minority of the asteroids in the main belt. Here we show that the non-family asteroids in the inner belt have orbital inclinations that increase and orbital eccentricities that decrease with increasing asteroid size. These correlations can be accounted for if both the non-family and the family asteroids originate from the disruption of a small number of large asteroids.  Separating the non-family asteroids into halo and non-halo asteroids allows us to estimate that 85% of all the asteroids in the inner main belt originate from the Flora, Vesta, Nysa, Polana and Eulalia families with the remaining 15% originating from either the same families or, more likely, a few ghost families. These new results imply that we must seek explanations for the differing characteristics of the various meteorite groups and the near-Earth asteroids in the evolutionary histories of a few, large, precursor bodies. These results also support the model that asteroids formed big through the gravitational collapse of material in a protoplanetary disk. 

Disks around FU Orionis-type young eruptive stars as viewed by ALMA in the dust continuum

Cruz-Saenz de Miera, Fernando

A long-standing problem of the general paradigm of low-mass star formation is the "luminosity problem": protostars are less luminous than theoretically predicted. One possible solution is that the accretion process is episodic. FU Orionis-type stars (FUors) are thought to be the visible examples for objects in the high accretion state. It is still debated what physical mechanism triggers the increased accretion in FUor disks and whether all young stars undergo FUor phases. Recently, more and more studies suggest that some FUor disks are smaller and less massive than previously believed (Liu et al. 2018, Cieza et al. 2018), but for many objects, disk properties are still largely unknown. Motivated by this, in the framework of the Structured Accretion Disks ERC project at Konkoly Observatory, we conducted a deep, high spatial resolution (down to 20 au) 1.3 mm dust continuum survey of 10 FUors with ALMA. Here we present the results of our survey, including basic disk parameters, such as mass, size, spectral slope, possible asymmetries, etc. We detected all targets with high signal to noise ratio, and most of them seem very compact.  We compare our results with the requirements of outbursts in different theories. We also put our sample into context by comparing them with disk properties of non-outbursting sources from large ALMA surveys, to see whether FUor disks are special in any way or they are indistinguishable from the general disk population.

Spots, flares, accretion, and obscuration in the pre-main sequence binary DQ Tau

Kospal, Agnes

Pre-main sequence stars are intimately linked with their circumstellar material. This relationship manifests in a variety of phenomena that makes young stars highly variable at a wide range of wavelengths. The photometric variability of young stars can be traced back to four main origins: variable accretion, rotational modulation due to hot or cold stellar spots, variable line-of-sight extinction, and stellar flares. Here we present results on a very special young star, DQ Tau, which displays all of these effects. Thanks to the unprecedented precision of Kepler K2 and Spitzer data, we could separate the signature of the individual effects. DQ Tau is a young low-mass spectroscopic binary, consisting of two almost equal-mass stars on a 15.8 d period surrounded by a circumbinary disk. Our light curve analysis revealed that the rotational modulation appears as sinusoidal variation with a period of 3.017 d. In our model this is caused by extended stellar spots 400 K colder than the stellar effective temperature. During our 80-day-long monitoring we detected 40 stellar flares with energies up to 1.2 x 10^35 erg and duration of a few hours. The flare profiles closely resemble those in older late-type stars, and their occurrence does not correlate with either the rotational or the orbital period. We observe elevated accretion rate up to 5 x 10^-8 M_Sun/yr around each periastron. Our Spitzer data suggests that the increased accretion luminosity heats up the inner part of the circumbinary disk temporarily by about 100 K. We found an inner disk radius of 0.13 au, significantly smaller than expected from dynamical modeling of circumbinary disks. Interestingly, the inner edge of the disk is in corotation with the binary's orbit. DQ Tau also shows short dips of <0.1 mag in its light curve, reminiscent of the well-known "dipper phenomenon" observed in many low-mass young stars

A Study of Inner Disk Gas around Young Stars in the Lupus Complex

Arulanantham, Nicole

We present a study of molecular hydrogen at the surfaces of the disks around five young stars in the Lupus complex: RY Lupi, RU Lupi, MY Lupi, Sz 68, and TYC 7851. Each system was observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST), and we detect a population of fluorescent H2 in all five sources. The temperatures required for LyA fluorescence to proceed (T ~ 1500-2500 K) place the gas within ~15 AU of the central stars. We have used these features to extract the radial distribution of H2 in the inner disk, where planet formation may already be taking place. The objects presented here have very different outer disk morphologies, as seen by ALMA via 890 micron dust continuum emission, ranging from full disks with no signs of cavities to systems with large regions that are clearly depleted (e.g. TYC 7851, with a cavity extending to 75 and 60 AU in dust and gas, respectively). Our results are interpreted in conjunction with sub-mm data from the five systems in an effort to piece together a more complete picture of the overall disk structure. We have previously applied this multi-wavelength approach to RY Lupi, including 4.7 micron IR-CO emission in our analysis. These IR-CO and UV-H2 observations were combined with 10 micron silicate emission, the 890 micron dust continuum, and 1.3 mm CO observations from the literature to infer a gapped structure in the inner disk. This single system has served as a testing ground for the larger Lupus complex sample, which we compare here to examine any trends between the outer disk morphology and inner disk gas distributions.

Magnetic Variability of the Sun over the Main Sequence Lifetime

Nandi, Dibyendu

The Sun's magnetic output varies and this variation impacts its radiative and wind output, and spawns magnetic storms such as flares and coronal mass ejections. Several decades of observations and modelling in the context of the solar system show that solar variations force planetary environments and atmospheres. It is thought that the magnetic output of the Sun has evolved over timescales relevant for planetary evolution, driven by changes in its internal differential rotation due to angular momentum losses mediated by the solar wind. Based on an analysis of available stellar activity observations and stellar parameters relevant for the solar dynamo, we infer the magnetic field variation of the Sun (or a solar-like G2 star) over its Main Sequence lifetime. In the light of this inferred magnetic variability of the Sun, we discuss plausible changes in our space environment over timescales relevant for habitability and planetary atmospheric evolution.

UX Orionis phenomenon in protoplanetary disks seen face-on

Demidova, Tatiana

The direct observations of protoplanetary disks showed that many images of the disks had a large-scale asymmetry. Such an asymmetry may be observed even if a protoplanetary disk is seen face-on. The inhomogeneous distribution of the matter or anistropic illumination of the disk surface can be responsible for the asymmetry. The perturbations in the disk can be caused by the orbital motion of a massive planet or substellar companion. Streamsofmatter, densitywaves and vortixes may arise in the disk and affect the photometric properties of the disk. For instance, the variable circumstellar extinction is produced in the disks seen edge-on or at the small angle to the line of sight (UX Ori phenomenon). Theinnerpartofthediskmay bewarpedbecauseoftheinclinationofthecompanionorbittothediskplane. The warp prevents the spread of stellar radiation in some direction. The effect can be observed in optical and NIRspectrum because only the surface layer heats up and cools quickly enough for the rotating disk.To research the phenomena we consider the model of an young star with a protoplanetary disk and a low-mass companion (q = M1:M2= 0.1), which orbit is inclined to the disk plane. Thesetofthemodelsofsuchasystem was calculated forthewiderangeoftheparametersbySPHmethod, with taking into account the temperature distribution along the radius and height. On the basis of hydrodynamic modelswe simulated the optical and NIRimagesof protoplanetary disks seen face-on. The simulations show the outer part of the disk has the bright and shadowed domains, located not symmetrical with respect to the line of nodes. The shape and size of the shadow depend on the model parameters. For all models the bright and dark domains do not follow the companion, but make small amplitude oscillations with respect to the some direction. The properties of the described model open new opportunities of searching low-mass companions in the vicinity of young stars.

Resonant multi-lane patterns in circumbinary young debris disks

Demidova, Tatiana

Formation of resonant multi-lane patterns in circumbinary young debris disks with planets is considered in a set of representative massively simulated models. We find that the long term-stable resonant patterns are generically formed, shepherded by embedded planets. The patterns are multi-lane, i.e., they consist of several concentric rings. Statistical dependences of their parameters on the planetary orbital parameters are recovered. Relevant additional massive simulations of planetesimal disks in systems with parameters of Kepler-16, Kepler-34, and Kepler-35 are accomplished and described. We find that co-orbital patterns generically form in systems with moderate orbital eccentricities of the binary's and planetary orbits (like in Kepler-16 and 35 cases). We argue that any observational identification of characteristic resonant ring-like patterns in disks of the considered class may betray presence of planets shepherding the patterns. This work was supported by the Russian Foundation for Basic Research (projects Nos. 17-02-00028-a)

The Life of The Young Sun: Biogenic Conditions on the Early Earth and Mars

Airapetian, Vladimir

The physical environments of the young Sun can provide important clues for the origin of life on the early Earth and the potential for life on early Mars. According to recent observations of young stellar solar-like stars, our 0.7 Gyr-old Sun was a magnetically active star exhibiting frequent and energetic flares, coronal mass ejections (CMEs) and fast and dense wind, and thus extreme space weather environments. These extreme events should have impacted the atmospheres of the early Earth and Mars. In order to reconstruct space weather from the young Sun, we employed a data driven three-dimensional  magnetohydrodynamic Alfvén Wave Solar Model applied for k1 Cet, the best known young Sun’s proxy. Alfvén waves launched at the chromosphere dissipate into heat forming a hot and dense corona that emits intensively in EUV and X-ray bands and a fast and dense bi-modal wind.The fast wind emanating from the polar regions of the star interacts with slow wind associated with streamer belt and forms co-rotating interaction regions (CIRs) that develop into shocks. We also discuss our recent models of super-Carrington CMEs from the young Sun. The application of a 3D global magnetospheric models suggests that CME and CIR induced dynamic pressures and magnetic fields significantly perturbed the magnetospheres of the early Earth & Mars exposing 70% of their surfaces to energetic particles. Solar energetic particles accelerated on CIR and CME induced shocks could have contributed to the rise of prebiotic chemistry and the origin of life on these planets.

Carbon and oxygen abundances in dwarf stars of the Solar neighbourhood

Tautvaisiene, Grazina

Stars and planets form from the same material, thus some of their properties are expected to be inter-connected. In order to characterize exoplanets, we need to investigate the planet-hosting stars. Occurrence of different types of planets and their orbital parameters may depend on chemical abundances of their hosting stars. The study of carbon and oxygen in stars is crucial because these elements are quite abundant and play an important role in stellar interiors by generating energy in thermonuclear reactions. Abundances of C and O may influence water availability on exoplanets. The C/O ratio also controls an amount of carbides and silicates that can be formed. We are performing a uniform study of C/O ratios in a large sample of stars located towards the northern ecliptic pole which will be targeted by the TESS and JWST space missions. The first results for a sample of 140 stars analysed will be presented. 

Simultaneous Multi-band Transit Observations of Low Density Hot Jupiters

de Leon, Jerome

Observations of transiting exoplanets provide an invaluable window into the nature of exoplanet atmospheres. Characterizing an exoplanet atmosphere especially from the ground using meter-class telescopes however remain difficult. A promising method to detect broad atmospheric features is to search for Rayleigh scattering signature using multi-band photometry in the optical wavelengths. For this study, we used OAO/MuSCAT to conduct simultaneous multi-band observations of several transiting systems hosting low-density hot Jupiters including HAT-P-12b, HAT-P-14b, and WASP-21b. Our goals are (1) to improve the transit parameters of these systems, and (2) to search for broad spectral features such as Rayleigh scattering signature in the optical wavelengths. The derived transit parameters are in good agreement with previous results. Comparing the measured transit depths with the spectrum model for each planet, we found that our achieved photometric precision is not enough to robustly distinguish between the two atmospheric models. However, we found that HAT-P-12b and HAT-P-44b spectra are consistent with Rayleigh scattering. On the other hand, we found a positive slope for WASP-21b which cannot be explained by either atmospheric models. Motivated by our results, we consider future multi-epoch observations of these systems as well as search for new targets feasible for detecting broad atmospheric features using MuSCAT and MuSCAT2.

The effect of carbon grain destruction on chemical structure of protoplanetary disks

Wei, Chen-En

The bulk composition of Earth is dramatically carbon poor compared to that of the interstellar medium, and this phenomenon extends to the asteroid belt. A gradient in the amounts of refractory carbon relative to silicate is shown in our solar system. To interpret the carbon deficit problem, we focus on two issues: (1) The carbon depletion gradient in the inner solar system. (2) Test the carbon grain destruction observationally.We assume two kinds of central stars T-tauri star and Herbig Ae star for the former and the latter issues, respectively. The results of the chemical models with and without the carbon grain destruction show significant differences especially near the midplane in the inner disk, where CO gas is abundant and not photodissociated. Carbon bearing species, e.g., HCN, become abundant while oxygen bearing species, e.g., H2O, becomes less abundant in the model with carbon grain destruction inside 2 au near the midplane in the T Tauri disk. Meanwhile, we calculate the solid carbon fraction relative to the total elemental abundance of carbon as a function of radius in the inner disk. In the model without carbon grain destruction, the ratio is about 75 % and doesn’t change very much at different radii since the majority of the carbon is locked in the refractory form. In the model with carbon grain destruction, the solid carbon fraction decreases in the inner disk as icy carbon-bearing species evaporate into gas inside their snowlines.  However, in order to match the gradient in the solid carbon fraction in our solar system quantitatively, we will need a more comprehensive model.Furthermore, we consider HCN and its isotopologue, H13CN, as our candidate tracer of the carbon grain destruction, and make a prediction for the ALMA observations. The results indicate the difference in the HCN/H13CN line emitting regions as well as their intensity ratio are useful tracers of the carbon grain destruction. 

Anomalous distributions of deuterated formaldehyde in the low-mass protostar L1527

Yoshida, Kento

We present our works on anomalous distributions of deuterated molecular species found in the Class 0 low-mass protostar L1527. From ALMA observations, we have recently found that the distributions of formaldehyde (H2CO) and the deuterated species (HDCO and D2CO) are clearly different from each other. The emission of H2CO is concentrated on the vicinity of the protostar (r<250 au), indicating the efficient evaporation from dust grains. On the other hand, the deuterated species mainly reside in the outer envelope (r~1000 au), and do not show the emission from the vicinity of the protostar. It has been believed that H2CO and its isotopologues are produced not only in the gas-phase but also on dust grains and released into the gas phase in the warm region near the protostar (T>40 K). This process is indeed the case for H2CO, because its distribution is concentrated around the protostar. On the other hand, our result indicates that the deuterated species are not. According to their distributions, they are likely produced in the gas phase and/or released from dust grains via non-thermal processes in the outer envelope. The D/H ratios in the outer envelope are derived to be high (D2CO/HDCO~30%) in comparison with the other species reported so far (~a few percent in this source). Isotope ratios in molecules can vary along the evolution from interstellar clouds to protostars. As shown above, detailed comparisons of distributions of the isotopic ratios will be useful for understanding how such an evolution in the molecular isotopic ratios occurs. Furthermore, such studies can be extended to disk-forming regions with ALMA, which will provide us with rich information bridging the interstellar chemistry and the planetary chemistry.

ALMA Observations of Sulfur-bearing Molecules in Protoplanetary Disks

Nomura, Hideko

Protoplanetary disks are the natal place of planets and ALMA observations are now revealing the physical and chemical structure of planet forming regions in the disks. Understanding chemical components of gas, dust and ice in the disks is essential to investigate the origins of materials in the plants. Meanwhile, molecular lines are useful to trace physical properties of astronomical objects. Sulfur-bearing molecules are known as shock tracers and have been recently observed around protostellar disks surrounded by infalling envelope (e.g., Sakai et al. 2017, Miura et al. 2017). I will report the result of our ALMA observations of sulfur-bearing molecules towards ten T Tauri disks in the Taurus molecular clouds. It is thought that eccentricities of planetesimals are excited due to gravitational interaction with (proto)planets in protoplanetary disks. As a result, bow shocks are formed around the icy planetesimals and they evaporated via the shock heating. The evaporation rates and orbital evolution of such icy planetesimals have been investigated (Tanaka et al. 2013, Nagasawa et al. 2014). In this work we aimed to observe the molecules evaporated from icy planetesimals with ALMA as a possible tracer of (proto)planet formation in the disks. We selected transition lines of sulfur-bearing molecules as a tracer; however, the lines were undetected by our observations, unfortunately. The obtained upper limits of the line intensity give us some information, thanks to high sensitivity of ALMA. Based on the observed upper limits and model calculations, we discuss the fractional abundances of sulfur-bearing molecules in the ice mantle on grains in the outer regions of the disks and their relation with those observed in comets in our Solar System as an analogues of comparison between the fractional abundances of complex organic molecules recently found in protoplanetary disks and those found in comets (e.g., Oberg et al. 2015; Walsh et al. 2016).

Nitrogen-included carbonaceous Compounds (NCC): Laboratory-synthesized organics as the probable candidate for the carrier of the UIR bands observed in dusty classical novae

Endo, Izumi

The unidentified infrared (UIR) bands have been observed ubiquitously in various astrophysical environments. PAHs (polycyclic aromatic hydrocarbons) are often used as a likely candidate of the band carriers to interpret the behavior of the observed UIR bands, however, our knowledge on the true carriers of the UIR bands is still limited. We have experimentally synthesized Nitrogen-included Carbonaceous Compounds (NCC) by exposing Quenched Carbonaceous Composites (QCC; Sakata et al. 1983, Nature, 301, 49) to nitrogen plasma via 2.45 GHz microwave discharge and examined its infrared properties. Infrared absorption spectra of NCC exhibit a broad feature around 7.9µm, which is remarkably similar to the “Class C” UIR bands observed at classical novae (e.g., V2361 Cyg). Our plasma chemical vapor deposition (CVD) method to synthesize NCC well simulates the process of dust formation/evolution in nova outburst ejecta. In the process of dust condensation in stellar ejecta from evolved stars, nitrogen inclusion into carbonaceous dust can naturally occur. Moreover, a high nitrogen content in nova shells is often reported (Dalgarno & Escalante 1989, RMxAA 18, 184). The N/C ratio (atom) of NCC is 4.1-5.3% from the measurement with EA/IRMS (Elemental Analyzer/Isotope Ratio Mass Spectrometer) at JAMSTEC (Japan Agency for Marine-Earth Science and Technology). X-ray Absorption Near Edge Structure (XANES) analysis of NCC indicates that amine and imine structures are included in the NCC. We conclude that the 7.9µm feature of NCC is attributed to aromatic and/or aliphatic amine. The remarkable similarity between the infrared properties of NCC and the UIR bands observed in classical novae suggests that the NCC, which has amine structure and contains N/C=4-5% of N atoms, is a strong candidate of the carrier of the UIR bands formed around some dusty classical novae. We will also discuss a potential link between NCC and Insoluble Organic Matter (IOM) in meteorites.

Multiple paths of deuterium fractionation in protoplanetary disks

Aikawa, Yuri

Molecular D/H ratios, such as HDO/H2O, are higher than the elemental D/H ratio in the primordial material in the Solar System, as well as in Earth’s ocean. This rather ubiquitous deuterium enrichment could originate in chemical reactions in cold environment such as molecular clouds and outer regions of protoplanetary disks, where the difference in zero-point energies between the normal and deuterated isotopologs stands out. While molecules are already deuterated in molecular clouds, the high D/H ratios of molecular ions indicate that deuteration proceeds in disks, as well. Spatial distributions of line intensities vary among deuterated species, which suggests that they have different deutration paths. Observations, however, show that their distributions also vary among disks. Motivated by these observations, we calculated a gas-grain chemical reaction network in protoplanetary disks to investigate the major deuteration paths and their dependence on disk parameters such as grain size and turbulence. Our network model includes spin-state chemistry, which is known to affect deuteration. We found multiple paths of deiuterium fractionation; exchange reactions with D atoms, such as HCO+ + D, are effective in addition to those with HD. If grains are small, freeze-out is severe in the cold midplane, while the disk surface is shielded from UV radiation to be relatively molecule-rich, which tends to make the radial distribution of molecular column density flat. As grains grow, photodissociation dominates in the disk surface, while gaseous molecules in the midplane are enhanced and contribute to line emissions. Turbulent diffusion transports D atoms and radicals at the disk surface to the midplane, and stable ice species in the midplane to the disk surface. The effects of turbulence on chemistry are thus multifold. We also derive the analytical formulas for abundances of H3+, HCO+, N2H+ and their deuterated isotopologues in the cold midplane.

RCW98: a dust enshrouded HII region

Ehlerová, Sona

We present observations of the warm ionized gas in the HII region RCW98 and combine them with images of this region at other wavelengths (dust, CO and HI). Using the thin shell approximation we construct the simple model of this warm bubble and compare it with the radiation and mechanical energy released by young stars inside the HII region.

Searching for chemical signatures of planet formation

Rab, Christian

In the last couple of years, high spatial resolution observations of protoplanetary disks have revealed structures such as gaps, rings, vortices and spiral arms. Those structures are probably signposts of ongoing planet formation indicating that protoplanetary disks are actually already planet-forming disks.Most of these structures have been detected using telescopes such as ALMA and SPHERE by observing the dust component, and it is not clear to what extent the gas follows the dust distribution and to what extent those structural features impact the chemistry in planet-forming disks. We model those three-dimensional structures using the 3D dust radiative transfer model MCMax3D and the thermo-chemical model ProDiMo (PROtoplanetary DIsk MOdel). With such an approach it is possible to infer self consistently the physical and chemical conditions at the location of ongoing planet formation such as inside a gap. Via synthetic observables for the dust and the gas, a direct comparison of the models to existing and future observations is also possible. This allows for deriving stringent constraints on properties such as the gas to dust ratio, temperature and chemical composition of the gas and the solids.We present first exemplary results for models with vortices, gaps and embedded planets. With those models we aim for answering questions such as: are the observed dust gaps also depleted in gas, and if yes to what extent; do dust overdensities have a significant impact on the gas-phase and ice chemistry and are planets required to explain those structures. Answering those questions provides stringent constraints for planet-formation theories and initial conditions for the formation of planetary atmospheres. We also discuss what we can already learn from modelling of existing observations and what kind of observations are required to provide further constraints on the planet formation process.

The abundance distributions of [a/Fe] in the Galactic disk giants from the LAMOST DR4

Li, Ji

Disk is the main structural component of the Milky Way, but whether there are sub-structures such as the so-called thin- and thick- disks has always been a controversial issue. The LAMOST Spectroscopic Survey of the Galactic Anti-center (LSS-GAC) provide the largest and most complete sample stars to investigate the disk structure of the Galaxy. Using the Add Value Catalogue V2 of LSS-GAC, we investigate the abundance  distribuations of [a/Fe] ratios in the R-z space for 775 091 disk giants from the LAMOST DR4.  Our results show that the sample stars can be seperated into two chemical distinct populations the thin- and thick- disks with the a-low and a-high abundances, respectively. While the chemical seperated thin and thick disc components are overlaped considerably in spatial kinematics in solar neibourhood.  Moreover, our results indicate the Galactic disk is edge thickening both for the thin- and thick- disks. 

Steady orbits of Small Solar System bodies and some aspects of Alfven-Arrhenius concept about evolution of Solar system

Kolomiyets, Svitlana

In connection with the accumulation of a huge amount of new observational data on the Solar system and exoplanets, the introduction of modern information technologies in the methods of researching a large amount of data, and also with obtaining new knowledge about the Universe, it is time to turn once again to some theories of the past about the structure and evolution of planetary systems. There was the Alfven-Arrhenius concept about the structure and evolution of the Solar system (Alfven&Arrhenius 1998). For the researchers of Small Solar system bodies, the Alvfen-Arrhenius concept is attractive in that it pays much attention to the analysis of the origin and development of the class of small bodies of the Solar system (asteroids, comets, meteoroids). We have examined some aspects of the Alfven-Arrhenius concept regarding the evolution of small bodies. The purpose of our study was to identify in the distributions of selected elements of the orbits of small bodies of the Solar System a fine deterministic structure associated with the evolution of their orbits. For this purpose, the distributions of orbital elements of near Earth objects (Near Earth Asteroids - NEA, Near Earth Comets - NEC and meteoroids in the Earth's atmosphere) were analyzed. To analyze the selected data, a modified method was used to extract a useful signal from a noisy sample and some other methods (Cherkas et al. 2014). As a mathematical model, a time series model was adopted. It can be said that the conducted research does not deny the existence of steady periodicity in the distribution of our samples of Small Solar system bodies (ie, the presence of regions with an increased and lower concentration of their orbits). There are grounds to assert that not only the process of decay of larger bodies into smaller components can occur in the Solar system, but also the formation of steady orbits on which the accretionary aspect of the Alfven-Arrhenius concept (substance pooling) looks quite logical.

Rising magnetic flux tubes as a source of IR-variability of the accretion disks of young stars

Khaibrakhmanov, Sergey

We investigate the dynamics of the magnetic flux tubes (MFTs) in the accretion disks of young stars. Slender flux tube approximation is used. Equations of the model include the aerodynamic and turbulent drag forces, radiative heat exchange with external medium, magnetic pressure of the disk. Structure of the disk is calculated using our MHD model of the accretion disks of young stars. Vertically stratified polytropic disk is considered.We study various thermal regimes of the dynamics of the MFT: motion in thermal equilibrium with external gas, adiabatic motion, motion with heat exchange. We investigate dependence of the velocity of the MFTs on initial radius, plasma beta, position in the disk.Simulations show that the less initial plasma beta of the MFT the more it’s speed. The MFTs with plasma beta ~0.1 and radius comparable to height scale of the disk move with velocities up to 50 km/s causing periodic outflows from the disks. Pressure of the magnetic field of the disk counteracts the buoyancy causing the MFTs to oscillate near the surface of the disk. Periods of the oscillations are 10-100 days. The radius, density and temperature of the MFTs also vary during the oscillations.We propose that the MFTs periodically rising from the inner regions of the disks and oscillating above the disk’s surface can cause the IR variability of the thermal radiation of the disks. Time scales of oscillations found in our simulations agree with the measured periods of the IR variability of the accretion disks of young stars.

Spectroscopic and photometric survey of the northern sky: Towards understanding of the Galactic chemical environment in the Solar vicinity

Mikolaitis, Šarunas

A spectroscopic characterisation is available for less than 30% of bright stars in the Solar neighbourhood leaving us with missing information about the Galactic environment in this region of space. This is very unfortunate for astero-seismic and planetary studies. For example, new space missions (e.g. NASA-TESS or ESA-PLATO) will perform an in-depth analysis of large fields of the sky-sphere searching for extraterrestrial planets around bright stars that are similar to the Sun. In order to achieve thier goals, the space missions need a full characterisation of observational objects. However, large spectroscopic surveys that have the greatest input in studying properties of Solar environment and far beyond, usually exclude brightest nearby stars. In this study, we aim to observe high-resolution spectra for all bright (V < 8 mag) and cooler than F5 spectral class dwarf stars in the northern-most fields of the sky sphere in order to determine their precise atmospheric parameters and abundance patterns with spatial and temporal distribution. We use high-resolution spectra obtained with the VUES spectrograph mounted on the 1.65 m telescope at the Moletai Astronomical Observatory of the Institute of Theoretical Physics and Astronomy, Vilnius University. High-resolution spectra (R = 60 000) were observed in two fields with radius of 20 degrees towards the northern ecliptic pole which will be targeted by the TESS and PLATO space missions. For 73% of the observed stars we spectroscopically determined the main atmospheric parameters and chemical properties for the first time. We used magnesium to iron and magnesium to manganese ratios for tagging Galactic substructures in the solar vicinity for further investigations.In this contribution, we put together stellar atmospheric parameters and chemical compositions with the derived ages and orbital parameters to draw a chemical picture of the very close Solar vicinity.

ALMA Study of the Envelope and Outflow Rotation in the young Classs 0 Protostar B335

Etoh, Yuki

To reveal how protoplanetary disks, precursors of planetary systems, are formed around protostars, we have analyzed ALMA archival data of the young Class 0 protostar B335. We have identified the rotating motion of molecular gas around the protostar, furthermore, a sign of the flip of the rotational vector, “counter-rotation”. These results should reflect the earliest stage of the disk formation around B335. The molecular outflow as seen in the 12CO (2-1) emission in B335 consists of small (~100 au) “bullets” and symmetric “parabolas” along the east-to-west direction. The moving velocities of the bullets reach ~200 km s-1, much faster than typical velocities of molecular jets driven by low-mass protostars. The dynamical time of those jets is estimated to be as short as 15 years. Those results indicate the possibility that we will be able to obtain real time movie of the motion of the bullets with additional ALMA observations. Furthermore, both of the bullets and parabola exhibit rotation, implying the extraction of the rotational angular momenta from the circumstellar disk. In this presentation, we will report these results and discuss the anticipated results which will be obtained with the future ALMA observations.

Large-scale magnetic field of the accretion disks of T Tauri stars

Dudorov, Alexander

We investigate the large-scale magnetic field in the accretion disks of young stars [1]. Our MHD model of the accretion disks include equations of Shakura and Sunyaev, induction equation with Ohmic diffusion, magnetic ambipolar diffusion, buoyancy and the Hall effect, equations of thermal and shock ionization.Our calculations show that the magnetic field in the accretion disks of young stars has complex geometry. The magnetic field has quasi-azimuthal geometry in the inner regions, where thermal ionization operates. Magnetic buoyancy hinders amplification of the magnetic field in this region. Inside the ``dead’’ zones, the magnetic field geometry is quasi-poloidal due to efficient Ohmic diffusion. Depending on the ionization intensity and dust grains parameters, magnetic field can have quasi-radial or quasi-azimuthal geometry in the outer disk regions, where magnetic ambipolar diffusion hinders amplification of the radial component of the magnetic field. The Hall effect leads to transformation of the toroidal magnetic field into the poloidal one near the borders of the ``dead’’ zones.Our model predicts that magnetic field strength near the inner boundary of the disks of T Tauri stars is 10-100 G, which is comparable with the stellar magnetic field. Typical magnetic field strength at 3 au is 0.1-1 G, in agreement with measurements of meteorites remnant magnetism. Plasma beta is not constant throughout the disk, according to our model.We made synthetic maps of dust emission polarized due to the dust grain alignment by the magnetic field. We show that the ‘dead’ zones can appear in the polarization maps as the regions with the reduced values of polarization degree.References1. Khaibrakhmanov S., Dudorov A., Parfenov S., Sobolev A. MNRAS. 2017. V.464. P.586.

Violation of the paradigm: a new path of circumstellar disk evolution around young A-type stars

Moor, Attila

In the early phase of their evolution stars are surrounded by massive primordial disks, mainly composed of gas but also containing a lesser amount of dust. According to the current paradigm, this primordial material dissipates by the age of 10 Myr in most systems, leaving behind a tenuous debris dust disk, whose observable parts are composed of short-lived second generation dust grains that are replenishedfrom collisional erosion or evaporation of larger planetesimals. While the evolution of dust between the two stages is rather well studied, the evolution of gas remains poorly explored. In order to better understand this aspect of the transition, we carried out observations with ALMA to measure the CO content of 18 nearby young (10-50 Myr) dust rich debris disks. We discovered gas in three debris disks.By supplementing our target list with literature/archival CO line data, we compiled a nearly complete volume-limited sample of dust-rich cold debris disks with fractional luminosity of >5x10-4 within 150pc.The analysis of this sample implied that the presence of CO gas in bright debris disks around young A-type stars is a common phenomenon. Interestingly, dust-rich debris disks around young FG-type stars exhibit a significantly lower gas incidence. The main difference between the two samples is related to a special population of gaseous debris disks whose total CO gas quantity is comparable to that of less massive Herbig Ae and T Tauri disks. This large amount of gas indicates that - contrary to "normal" debris disks where the gas component is derived from the erosion of planetesimals - in these objects the gas may rather have primordial origin. Since their dust content is secondary, these disks probably have a hybrid nature representing a very special phase in which the evolution of the gas component is decoupled from that of the dust.

Icy-Grain Aggregation at the Earliest Stages of Planet Formation

Fraser, Helen Jane

Water is incorporated into protoplanetary disks in the form of icy interstellar grains, dominated by amorphous water ice. Ice provides most of the mass available for planet formation beyond the snowline, and the eventual water content of terrestrial-type planets depends upon this reservoir. The first stage of terrestrial planet formation is the accumulation of icy nm to mm-sized interstellar grains into mm-grains, held together by van der Waals forces; dm to m scale ‘pebbles’ then clump together through streaming instabilities and form gravitationally-bound ‘pebble clouds’.  However, the collisional properties of icy aggregates in the mm – dm range are currently entirely unknown; hypo-velocity collisions between icy grains under these conditions are thought to be key to building up a critical mass of icy ‘pebbles’; the ice structure, phase and surface properties may also be relevant.We have studied the outcomes of low-velocity binary collisions between dust or icy grains in parabolic-flight experiments, showing that dust fragments more easily when 'cold', that mm to cm-sized icy grains bounce rather than stick in hypo-velocity collisions, and chemical impurities cannot aide ice sticking. We have exploited the ISIS neutron scattering source to understand the molecular- and mesoscale- structure of interstellar water ice. Our findings demonstrate why there are such a variety of collisional outcomes in laboratory experiments on "ice grain sticking". In conditions far from those found in protoplanetary disks, surface wetting and structure dominate the collisional outcomes. Conversely, under low density and temperature conditions the icy particle surfaces remain intact. By looking at sublimation and outgassing of the icy grains we are building a picture of the complex interplay of icy grains and the gas and dust, right at the "snow zone" where the critical onset of planet formation occurs. 

KAGONMA:NH3 mapping observations of molecular clouds with Nobeyama 45-m telescope

Murase, Takeru

In the molecular cloud collapsing phase, the molecular gas temperatureis a key to understand the process from a dense molecular cloud tostars. Thank to many transitions in the rather narrow frequency band,or 23 GHz, we can derive many physical parameters of molecular gasusing NH3 lines. From the line intensity ratio of the satellite andmain lines we can estimate the optical depth of the line and theintensity ratio of NH3 (1,1) and NH3 (2,2) we can estimate the rotationtemperature. This is well known and many investigations have been made.However, most of them are observations toward cores in molecularclouds. But our group made mapping observations of molecular cloudassociated with Monkey Head Nebula and W4 and no systematic temperaturegradient was found in either cloud (Chibueze et al. 2013 and Nakano etal. 2017). This shows mapping observation is important. Therefore, weconduct “KAGONMA”, which is an abbreviation of “Kagoshima Galacticobject survey with Nobeyama 45-m telescope in ammonia lines”. Based onC18O (1-0) data from FUGIN, or “FOREST unbiased galactic plane imagingsurvey with Nobeyama 45-m telescope”, we choose 71 molecular cores andare making mapping observations in NH3 (1,1), (2,2), (3,3) and H2Omaser lines. Until this season we have made 3 maps. From these maps wefound temperature structure in a cloud. In this talk we show the latestresults of them and discuss on the relation between temperaturestructure and star formation activity in each cloud.

Interactions of solid bodies with atmospheres of protoplanets

Dorfi, Ernst

During the formation of earth-like planets within protostellar disks the accretion of solid bodies plays an essential role in shaping the final planet. Usually the deposition of kinetic energy is simplified by the accretion luminosity L = GMplMacc/Rpl when the bodies, in-falling at a rate of Macc release their kinetic energy at the planets radius Rpl. We investigate this process in more detail because the protoplanets embedded in the gaseous disk are characterized by an extended atmospheres up to the Hill radius. We have developed a simple model for tracking the mass loss, the temperature structure and the break-up of an incoming planetesimal. Even solid bodies of sizes up 10km are stopped or melt by the frictional dissipation and explode into smaller fragments during their flight. In such cases the atmospheric gas is directly heated well above the planetary surface located at Rpl. In addition to this thermal input the release of dust particles modifies the opacity and thereby the overall stratification and extension of the planetary envelope. A large number of computations show how a size distribution of planetesimals generate a vertical heat source depending on the total accretion rate, the velocities at the Hill radius as well as the properties of the planetesimals. We further discuss the influence of the accretion history of planetesimals during building up the final core mass.

Infrared extinction in Orion A

Meingast, Stefan

Despite numerous studies in recent years, the characteristics of the infrared extinction law remain a controversial topic. Examples for open debates are the origin of the often-observed gray distribution of the MIR portion from ~3 to ~6 µm, as well as the the universality of the extinction law in the NIR regime (~1 to 2.5µm). Most recent studies, however, are relying on measurements toward the galactic center. There, multiple, physically separate, regions overlap along the line-of-sight. As a consequence, physical conditions along the observed direction can hardly be controlled, therefore biasing attempts to derive general characteristics of the extinction law.In this talk I will present new results on the infrared extinction law from 1 to 25 µm toward the Orion A star-forming complex. The Orion A molecular cloud is situated in the direction of the galactic anti-center, is located below the galactic plane, and furthermore appears to be well-isolated from other star-forming regions. At the same time, the cloud is relatively nearby (400pc) and features a large dynamic range in column densities. Moreover, the complex hosts a massive cluster, along with many other isolated star-forming events. Together, these conditions make it ideal to probe the extinction law in a controlled environment.Based on a statistically refined analysis, I will show that the extinction law does indeed vary across the molecular cloud. In particular, and in contrast to many results in the literature, this study finds direct evidence that the NIR portion is not universal and also determine the MIR portion of the extinction law to be variable. These variations show a strong spatial correlation where regions far away from the massive stars show a distinctly different extinction law compared to the immediate warm environment close to the cluster. Our evidence therefore points to the conclusion that feedback from the massive stars in the cluster can have a direct impact on dust grain properties.

Early solar system physical conditions and the origin: compatible models

Ragulskaya, Mariya

The origin and development of life on Earth was determined not only by conditions on the earth, but also by processes on the Sun and in the Solar System (SS). Significant factors for the early biosphere: 1. Radiation of the early Sun 2. Interdependence of the planets SS 3. Magnetic field of the Earth 4. Galactic cosmic rays (GCR).Young Sun (YS) had a circulation period of ~ 8 days, a mass of ~ 103% of the modern. The intensity of sporadic radiation exceeded the current one by several orders. The intense UV radiation of YS exerted a significant influence on the biosphere formation. The luminosity of YS was less by 30%. Then the surface of the Earth must be frozen. However, according to geological data, the temperature of the Earth's surface exceeded the modern. The paradox’s solution can lie in other reflection and absorption by the early Earth. The existence of biological films on the oceans’ surface is reported. They significantly altered the albedo of the planet and the composition of the atmosphere. Also, the early Earth could be closer to the Sun due to the migration of Jupiter and Saturn.The geomagnetic field (GF) protects the biosphere from intense cosmic rays. The formation of the GF occurred 2 billion years ago according to dynamo theory. According to paleomagnetic data there already was a magnetic field of the Earth 4.2 billion years ago. Its values were comparable with modern. The reason for the emergence of such a field could be the process of formation of the Earth-Moon system as well as tidal interaction of proto-Earth with migrating giant planets.The influence of space weather factors on the biosphere are observed to the present day. Saccharomyces cerevisiae strain Y-517 was studied by daily measurements in 2000-2012. During a minimum of solar activity, a significant contribution to the dynamics of cellular structures is made by GCR. At the maximum, the influence of solar activity and variations of the geomagnetic field are expressed.

An Unbiased High-Contrast Near-Infrared Imaging Survey of Nearby Herbig Ae/Be Stars: Are All Group I Disks Transitional?

van den Ancker, Mario

The process of clearing the disks surrounding pre-main sequence stars is still not well understood. Several competing theories have been proposed, by which either the disk is cleared through photo-evaporation, or due to clearing due to dynamical interactions with newly formed planets. The group of intermediate-mass young stars known as Herbig Ae/Be stars (HAeBes) have been classified in two groups, depending on the strength of the far-infrared excess in their spectral energy distribution. (Maaskant et al. 2013, 2014) have proposed that the group I sources, which have a larger far-infrared excess, may all have gaps, which could indicate the presence of newly formed planets in their disks.This proposal predicts a larger extent of the disk in scattered light in group I sources compared to group II HAeBes. We have used SPHERE, the high-contrast adaptive optics system at the VLT, to test this hypothesis by observing a sample of 24 nearby HAeBes. Using a novel method to reduce speckle noise, we have spatially resolved six disks in this sample, allowing us to test the Maaskant et al. hypothesis. In addition we have detected four new companion candidates.

Accretion-Ejection MHD simulations in Protostars

Tsinganos, Kanaris

By using as initial conditions analytical self similar solutions for MHD outflows, we have modeled the magnetosphere of young, low mass, stars with a stellar jet surrounded by accretion columns and an equatorial static dead zone connecting the star to the disk. The use of analytical solutions as initial conditions allows to attain steady or quasi steady solutions within a few stellar rotations showing that such solutions are remarkably stable. The simulations are performed with the PLUTO code on supercomputers, such as OCCIGEN on GENCI.In the simulations we vary the ratio of the mass accretion rate to the mass loss rate and also the size of the static dead zone. We have found that by varying this ratio within a range of observed values, we obtain a bimodal final state. Either a state wherein the stellar jet is separated from the accretion zone by a relatively low density, force-free region is obtained, or, we get a state where the low density region is replaced by episodic mass ejection coming from the disk and bouncing on the stellar atmosphere, creating thus a type of coronal mass ejections. Hence, the presence of episodic magnetospheric ejection is not compulsory but it depends on the value of this ratio. It is interesting that  this ratio is similar to the observed range of ratios in T Tauri systems, i.e., for a mass accretion rate exceeding 15 to 20 times the mass loss rate. Thus, it is very likely that such a bimodal behavior may be observed in T Tauri environments. By further increasing the accretion rate, we are investigating the transition from the T Tauri to the FUOR systems. In that case we conjecture that the cylindrically collimated jet may be replaced by a conical wind, which can also be explored with the same numerical technique.

A physically motivated dense-core extraction technique applied to Herschel/Planck observations

Hasenberger, Birgit

The evolution of dense cores in molecular clouds represents the earliest stage in the formation process of stars and planets. We are able to observe this stage by using multi-wavelength observations in the far-infrared and sub-mm range, which allow us to map nearby molecular cloud complexes in their entirety and resolve the core population embedded within them. However, the lack of a physically motivated definition of dense cores resulted in the development of a variety of algorithms designed to extract cores from observational data. In the most commonly used algorithms, core boundaries are based on the two-dimensional morphology of structures in the available maps, rendering the physical interpretation of results challenging. In addition, comparisons between studies of core samples are inherently problematic if different core extraction methods are employed.I will present a new method to define core boundaries observationally, based on the physical properties of the material in a molecular cloud. We model the flux distribution along the line of sight by taking into account the extent of structures on the plane of the sky. Subsequently, we can estimate the energy budget of cloud material in terms of its gravitational and thermal energy. The balance between these two contributions defines the boundaries of our cores. We illustrate the advantages and caveats associated with this approach by applying it to observations of the Pipe nebula by the Herschel and Planck satellites. We study in detail the derived core properties of this cloud, in particular the distribution of core masses.With this tool at hand, we are able to consistently define core samples in nearby molecular clouds, allowing us to compare core properties within individual clouds as well as between clouds. The development of a physically motivated core extraction algorithm thus represents an essential first step towards a deeper understanding of the processes involved in star formation.

An UXor among FUors: Extinction-related Brightness Variations of the Young Eruptive Star V582 Aur

Abraham, Peter

V582 Aur is an FU Ori-type young eruptive star in outburst since ~1985. The eruption is currently in a relatively constant plateau phase, with photometric and spectroscopic variability superimposed. Here we will characterize the progenitor of the outbursting object, explore its environment, and analyze the temporal evolution of the eruption. We are particularly interested in the physical origin of the two deep photometric dips, one that occurred in 2012 and one that is ongoing since 2016. We collected archival photographic plates and carried out new optical, infrared, and millimeter-wave photometric and spectroscopic observations between 2010 and 2018, with a high sampling rate during the current minimum. Besides analyzing the color changes during fading, we compiled multiepoch spectral energy distributions and fitted them with a simple accretion disk model. Based on pre-outburst data and a millimeter continuum measurement, we suggest that the progenitor of the V582 Aur outburst is a low-mass T Tauri star with average properties. The mass of an unresolved circumstellar structure, probably a disk, is 0.04 M ?. The optical and near-infrared spectra demonstrate the presence of hydrogen and metallic lines, show the CO band head in absorption, and exhibit a variable Ha profile. The color variations strongly indicate that both the ~1 yr long brightness dip in 2012 and the current minimum since 2016 are caused by increased extinction along the line of sight. According to our accretion disk models, the reddening changed from A V = 4.5 to 12.5 mag, while the accretion rate remained practically constant. Similarly to the models of the UXor phenomenon of intermediate- and low-mass young stars, orbiting disk structures could be responsible for the eclipses.

Difference of the Gas Density Histograms in and out of spiral arms in Milky Way Galaxy

Handa, Toshihiro

Stars are formed from dense gas cores through the gravitational collapse. Before this stage less dense gas must be compressed and becomes denser. However, its mechanism is not clear. For example, Kennicutt-Schumidt law shows a correlation between amount of low density molecular gas traced by 12CO and star forming activity in a galactic scale, which means there should be some global relation between diffuse and dense gases. This is a way to understand “cosmic recycling of matter” completely. To address this issue directly we should investigate the density structure of the interstellar matter (ISM) in the galactic scale. Until now many investigators have focused on the spatial structure of ISM such as the core mass function. However, we make a statistical investigation, which ignores the local structure of ISM itself. This is another approach on the density structure. We call it “Gas Density Histogram (GDH)”, which is an observational counterpart of the probability density function (PDF) of the gas density of ISM if gas density structure is steady. We use “FOREST unbiased galactic imaging survey with Nobeyama 45-m telescope” (FUGIN), which is a large coverage survey in 12CO (1-0), 13CO (1-0), and C18O (1-0) with 15” resolution. Using the method of the kinetic distance estimation, we can also estimate the line-of-sight depth for each l-b-v voxel. Therefore, we can estimate the volume density of the voxel from the observed column density. The resultant GDHs show different shape from place to place in the Milky Way Galaxy; GDHs of the inter-arm regions show log-normal or similar to log-normal, but those in the spiral arm regions show log-normal with a bump in higher density or flat-top.

Variable dust in the inner disk of a Herbig Ae star spatially resolved by infrared interferometry

Chen, Lei

An essential step to understanding the evolution of protoplanetary disks is the study of objects that contain gaps or inner holes.  The pre-transitional disk around the Herbig star HD 169142 exhibits multi-gap disk structure, differentiated gas and dust distribution, planet candidates, which make it a valuable target for a case study of disk evolution.  An especially interesting phenomenon in the HD 169142 system is a fading at near-infrared wavelengths, which suggests that the inner sub-au dust is dissipating on an exceptionally short time scale of <= 10 years.  Using near-infrared interferometric observations with VLTI/PIONIER, we studied the inner dust, constraining both its radial location and the dust grain size in the years 2011-2013, when the object was already in its near-infrared faint state.  The observations with high spatial resolution of ?/B ~ 2 mas constrain the radial location of inner dust to be ~ 0.08 au from the central star.  Combining the spatial information with radiative transfer modeling, we find the observations best interpreted with optically thin gray dust, with grain size larger than 1 micron.  This information on grain size provides a hint of dust grain growth in this late-stage protoplanetary disk.  However, an alternative model with optically thick dust, in which smaller grains are possible, is also discussed.While the near-infrared fading of the object happened on a time scale much shorter than the lifetime of a protoplanetary disk, we speculate that this fading is part of a series of flux fluctuations due to a combination of unsteady dust replenishing and short-term dust dissipation.  We are carrying on follow-up studies of the object, aiming at constraining the dust properties at multiple epochs, in order to further reveal the mechanisms behind the near-infrared variability.  Here, I report our study using PIONIER observations and I will also present some results from our latest follow-up measurements.

Dynamic interaction of expanding plasmospheres of hot giant exoplanets with the stellar wind: On the transit spectra features

Khodachenko, Maxim

The interaction of escaping upper atmosphere of a hydrogen rich non-magnetized analogue of HD209458b with a stellar wind of its host G-type star at different orbital distances is simulated with a 2D axisymmetric multi-fluid hydrodynamic model. A realistic sun-like spectrum of XUV radiation, which ionizes and heats the planetary atmosphere, hydrogen photo-chemistry, as well as stellar-planetary tidal interaction are self-consistently taken into account. Two different regimes of the planetary and stellar winds interaction were modelled: 1) the “captured by the star” regime, when the tidal force and pressure gradient drive the planetary material beyond the Roche lobe towards the star, and 2) the “blown by the wind” regime, when sufficiently strong stellar wind confines the escaping planetary atmosphere and channels it to the tail. The model simulates in details the generation of energetic neutral atoms (ENAs) around the planet due to their acceleration by the radiation pressure and as a result of charge-exchange between the stellar wind protons and planetary atoms. These simulations enable calculating of the Lya absorption during transits of HD209458b and quantifying the major mechanisms responsible for its observed features. The calculations in a wide range of stellar wind parameters and XUV flux values showed that under the typical Sun-like star conditions the observed absorption at the level of 6÷8% can be attributed only to the non-resonant natural line broadening. For lower XUV fluxes, e.g., during the activity minima, the number of planetary atoms that survive photo-ionization and give the origin to ENAs, increases resulting in up to 10÷15% absorption at blue wing of Lya line, caused by the resonant thermal line broadening. It has been found, that the radiation pressure in all considered cases has a negligible contribution to the production of ENAs and the corresponding absorption.

Constraints of habitability for the young Earth in a highly eccentric orbit

Pilat-Lohinger, Elke

In the last twenty years, thousands of planets outside the Solar system have been discovered, with exoplanets in different environments. Of course we cannot expect to find an exoplanetary system fully resembling our Solar System. Therefore, we consider a Solar System type configuration where the young Earth moves in an eccentric orbit and approaches the Sun to distances closer than Mercury.We focus on the study of young Earth 1 billion years ago, when the Sun’s extreme UV (EUV) flux was about 5 times higher than the current radiation. In case of eccentric motion of the Earth, strong variations of the EUV flux would influence the evolution of the planet’s atmosphere because maximum values of the EUV radiation of about 50 times the current EUV flux would be possible.Taking into account a certain amount of Nitrogen in the atmosphere of such a young Earth, we study the non-thermal loss of N2 over a long time interval.  We therefore want to investigate  to what extent eccentric motion will influence the conditions of habitability of a terrestrial planet.

Circumstellar disk fragmentation and the origin of massive planetary companions and free-floating Jupiters

Kouwenhoven, M.B.N. (Thijs)

Most of the Sun's nearest neighbors are M-type stars or brown dwarfs. Constraining the origin of such systems, in particular of those of brown dwarfs hosting a brown dwarf or massive planet as a companion, remains a challenge. Here, we present circumstellar disk fragmentation as a possible mechanism for such systems, based on numerical simulations. Circumstellar disk fragmentation results in the formation of multiple companions of varying mass (from super-Jupiters to low-mass stars) in wide and highly unstable orbits. The decay of these systems results in the ejection of massive planets and brown dwarfs, and in frequent physical collisions. Billions of years after formation, the host stars are often left with none, one, or two companions, with a large variety of configurations, including two types of hierarchical triples with predictable (and measurable) orbital configurations. Despite the unknown frequency of occurrence, circumstellar disk fragmentation is able to predict many of the challenging stellar and substellar systems in the solar neighborhood, and provides predictions for the properties of hierarchical systems containing brown dwarfs and massive planets.

A photometric/spectroscopic modelling survey of FU Ori Objects with Herschel

Postel, Andreas

Episodic accretion plays a major role in the accretion history of young stars._x000D_ In particular, FU Orionis objects (FUOrs) undergo accretion outbursts during_x000D_ which the_x000D_ accretion rate rapidly increases from typically 10^-7 M_Sun / yr to 10^-4_x000D_ M_Sun / yr and stays high over time scales of several decades to hundreds of_x000D_ years. The origin of such accretion outbursts remains unclear and could be due_x000D_ to viscous-thermal instabilities in the disc, thermal instabilities induced by_x000D_ density perturbations due to e.g. a massive planet in the disc, tidal effects_x000D_ from close companions, a combination of gravitational instability and the_x000D_ triggering of the magnetorotational instability, or again accretion of clumps_x000D_ in a gravitationally unstable disc._x000D_ Herschel has observed 12 FUors with PACS and SPIRE in both photometric and_x000D_ spectroscopic modes. We will present results from our analysis, which combines_x000D_ Herschel and Spitzer data with ground-based data together with_x000D_ hydrodynamical simulations and thermo-chemical modeling using a modified_x000D_ version of the ProDiMo tool, with the goal to improve our understanding of_x000D_ episodic outbursts in the first steps of life of low-mass young stars.

Following the trail of water from interstellar space to inhabited planets with the Origins Space Telescope

Bergin, Edwin

The Origins Space Telescope (OST) is one of four mission concepts that NASA is exploring in advance of the next decadal survey in the United States.   OST has tremendous relevance for tracing the origins of the stars, planets, and life from first light to present day.  In this talk I will describe the latest mission concept,  which will have a circular 5.9m aperture with a cryogenically-cooled telescope.  The instruments will cover wavelength ranges from 5 to 400+ microns and include both spectrographs and imagers.  In the mid-infrared, a purpose-built spectrometer will constrain the atmospheric composition and thermal structure of temperate Earth-size worlds via the transit technique with the goal of detecting two distinct biomarkers (methane and ozone), along with water and CO2.  This suite of molecules will determine whether the atmospheres of these potentially habitable worlds are in disequilibrium -- the signature of life.   With its tremendous spectral grasp and superb sensitivity, OST will survey water, both gas-phase and ice, toward as many as a thousand sources spanning all evolutionary stages of star and planet formation from molecular clouds to YSOs to planet-forming disks.  OST will possess the capability to measure the water's distribution in planet forming disks through observation hundreds of lines from the ground state lines that probe beyond waters iceline to higher energy transitions that emit only from interior to the snowline.  OST can also sample the water content via a combined study using a unique far-IR tracer of the highly uncertain disk gas mass, hydrogen deuteride.  I will also discuss how OST will transform our knowledge of the origin of Earth’s water by extending the sample of cometary bodies with detections of the D/H fingerprint by over an order of magnitude.  

The Influence of Chemical Composition on Planetary Upper Atmospheres and Atmospheric Losses

Johnstone, Colin

The thermal and chemical structures of the upper atmospheres of planets are very important for determining how quickly atmospheric gas is lost to space. These structures are determined by a range of processes, including heating by stellar radiation, especially in X-ray and UV wavelengths, and cooling by IR radiation from molecules such as carbon dioxide. The importance of each of the relevant mechanisms depends sensitively on the atmospheric composition. In this talk, I will discuss different atmospheric chemical compositions, and how they influence the atmospheric heating and cooling. I will link this to atmospheric loss mechanisms and long term atmospheric evolution.

Magnetic field geometry and activity of sun-like stars

Boro Saikia, Sudeshna

Magnetic activity and stellar winds in sun-like stars are known to influence habitability conditions of an orbiting planet. Detailed observations and theoretical models of solar magnetic activity has been carried out in the past few decades. However magnetic field and stellar wind conditions in other Sun-like stars, with different stellar parameters, is not fully  known. We investigated the magnetic activity and large-scale magnetic field geometry of 50 Sun-like stars as a function of effective temperature and rotation. The magnetic field geometry information, reconstructed using Zeeman Doppler imaging (ZDI), were taken from the literature. The complexity of the large-scale field and the fraction of poloidal and toroidal field strength is    also determined. We show that the large-scale magnetic field of sun-like stars do not exhibit any drastic difference for stars with different effective temperature.  On the other hand rotation plays an important role, where strong poloidal field is detected for slowly rotating stars.  Our results are important to understand how the magnetic field geometries of sun-like stars can change the stellar wind conditions and affect the atmosphere of an orbiting planet.

Brightness variations of young Sun-like stars from ground-based and space telescopes

Zsidi, Gabriella

Young stellar object are stars in the early stage of their evolution. They often show photometric variability, which may be due to non-steady accretion from the circumstellar disk onto the star, but other physical processes, such as rotating cold spots or the transit of a dust cloud can also change the observed brightness of the star. Variability is well examined at optical wavelengths, but nowadays more and more infrared data are available as well. The wavelength dependence of the variability carries information on the physical cause of the changing brightness. Here, we examine seven T Tauri-type stars known for their large amplitude variability selected from the Campaign 13 field of the Kepler K2 mission. We complemented the K2 light curves by nightly multi-filter optical monitoring observations made with the 90 cm Schmidt telescope of Konkoly Observatory. In order to extend our wavelength coverage, cadence, and temporal coverage, we complemented these data with 3.6 and 4.5 micrometer infrared photometry obtained with a nightly cadence with the Spitzer Space Telescope. We constructed K2, B, V, R, I, and infrared light curves and investigated the brightness and color variations of our targets, to establish the origin of the variability and separate the different physical effects.

When our Sun was Young: Coronal X-ray, TR-Chromospheric UV Emissions, Flares and Winds of the Young Sun (and solar-type stars) and Effects on Hosted planets.

Guinan, Edward

Studies of young solar proxies (G0-G5 V stars), as part of the ``Sun in Time'' program, show that the young Sun was rotating over ten times faster than today. As a consequence, these young sola -type stars (including the young Sun) had vigorous magnetic dynamos and correspondingly strong coronal X-ray and EUV emissions and chromospheric FUV and UV emissions - up to several hundred times stronger than that observed for the present Sun. Also, observations of the youngest solar proxies indicate that the young Sun had frequent and powerful flares and most likely significant winds. This paper is an update of the earlier studies by Ribas et al. (2005: ApJ.,622, 680; Guinan and Engle (2009: IAUS, 258, 395) with the addition of data from more recent stellar wind and flare studies (see Guinan and Engle 2015: IAUGA 2255511;  Airapetian & Usmanov 2016: ApJ, 817L.,24; Pognan et al. 2018: arXiv180205153 and references therein). This study focuses the first ~4.5 billion years of the Sun’s post-PMS life and also applies to other solar-type stars.The recent results of the `Sun in Time'' program will be discussed that show the decline of solar X-UV fluxes, winds and flares with slower rotation and increasing age. The determination of the flare energies and frequencies and stellar winds based on recent studies are presented. We present our most recent Age-Rotation-Activity relations for solar-type stars that also can be used in the study of other solar-type stars with planets (e.g. tau Ceti). Also briefly discussed are some of the major effects that the young Sun's strong magnetic activity had on the photoionization, photochemistry, and erosion of paleo-planetary atmospheres as well as on the development of life on these planets.This research is supported by grants from NASA and NSF which we gratefully acknowledge.

Habitable Zones around K and M Dwarfs

Cuntz, Manfred

One of the most fundamental topics of exobiology concerns the identification of stars with environments suitable for life. Although it is believed that most types of main-sequence stars might be able to support some forms of life (especially extremophiles), special requirements appear to be necessary for the development and sustainability of advanced life forms. The focus of this presentation is an assessment of ionizing radiation impact from dwarfs of spectral types K and M.  Aspects taken into account include (1) the frequency of the various types of stars, (2) the rate of stellar evolution over their lifetimes, (3) the width of the circumstellar habitable zones (CHZs), (4) the strength and persistence of their magnetic dynamo generated X-ray—Extreme UV emissions, and (5) forcing associated with space weather. The advantages and shortcomings of K and M-type dwarfs are discussed in the view of observations and updated theoretical results.

Protostellar Interferometric Line Survey of the Cygnus-X region: PILS-Cygnus

Kristensen, Lars

Most stars, including our own Sun, form in dense stellar clusters with hundreds or thousands of other stars. These clusters show an incredibly rich chemistry, particularly near the forming young stars, where planets eventually form. Understanding the origin of this chemistry is important to study the process of star formation and determine the complexity of chemistry that can develop, particularly in terms of prebiotic molecules. To achieve these goals, star-forming regions are being surveyed both in terms of number and type of objects, and in terms of frequency coverage. The larger the source sample, and the greater the frequency coverage, the stronger the final conclusions regarding the formation of complex organic and prebiotic molecules are. Achieving both at the same (number of sources and frequency coverage) is traditionally expensive, but the SMA with its upgraded receivers and SWARM correlator is now overcoming this technological barrier, making it cheap to cover large frequency windows in one go. We have exploited these capabilities and will here present the initial results of the Protostellar Interferometric Line Survey of the Cygnus X star-forming region (PILS-Cygnus). The survey is done by observing the frequency range from 329-363 GHz with the SMA at an angular resolution of 1" (~1500 AU). 

NIR interferometric observation of DG Tau with VLTI/AMBER: evidence of temporally varying obscuration

Chen, Lei

DG is a T Tauri star showing multi-wavelength variability from the optical to MIR.  Using the near-infrared interferometor VLTI/AMBER, we studied the spatial structure of the object in near-infrared.  A large part of K-band light are found to arise from outside of 0.5 au from the central star, suggesting an origin as scattered light instead of warm emission.  This differs from a typical young star, in which the K-band light is dominated by direct stellar light and the warm emission from the disk rim, while scattered stellar light contributes only a small fraction (<20%).  The K-band visibilities measured by our observations are dramatically lower than previous results from Keck Interferometor, suggesting that the object was experiencing changes in brightness distribution.  We propose a scenario that the central star is obscured by temporally varying material.  With this scenario we attempt to self-consistently interpret several phenomena: the high fraction of scattered light, the changes in brightness distribution, and the multi-wavelength variability.  

Time-variability and disk geometry in Herbig Ae/Be disks

Szakats, Robert

Herbig Ae/Be stars are young, intermediate mass stars. They exhibit variability at optical and infrared wavelengths, whose physical origin is mainly related to their circumstellar disk. Accretion from the inner disk onto the stellar surface, or temporary increase of the extinction in the line-of-sight caused by passing circumstellar dust clumps are examples for these variability processes. Here we present new results from our coordinated multi-wavelength and multi-epoch observing campaign of nine Herbig Ae stars. The observations covered two weeks with daily cadence, obtaining optical BVRI, near-infrared JHK, and mid-infrared Spitzer photometric monitoring data. We used the data to outline the brightness and color variations during the observing period. One goal of our analysis was to document and understand the response of the inner disk on the changing irradiation by the central star. The intensity and color of the response can be interpreted in terms of the geometry of the inner disk. Another aspect of our study is to reveal the wavelength dependence during UX Orionis-type fading events, which provide direct information on the size of the obscured disk region. Our sample allows us to explore the similarities and differences among the disk structures of Herbig Ae stars, and will help to observationally test the various theoretical models of disk geometry. 

Mass transport from the envelope to the disk of V346 Nor: a case study for the luminosity problem in an FUor-type young eruptive star

Kospal, Agnes

A long-standing open issue of the paradigm of low-mass star formation is the luminosity problem: most protostars are less luminous than theoretically predicted. One possible solution is that the accretion process is episodic. FU Ori-type stars (FUors) are thought to be the visible examples for objects in the high accretion state. FUors are often surrounded by massive envelopes, which replenish the disk material and enable the disk to produce accretion outbursts. However, we have insufficient information on the envelope dynamics in FUors, about where and how mass transfer from the envelope to the disk happens. Here we present ALMA observations of the FUor-type star V346 Nor at 1.3 mm continuum and in different CO rotational lines. We mapped the density and velocity structure of its envelope and analyze the results using channel maps, position-velocity diagrams, and spectro-astrometric methods. We found that V346 Nor is surrounded by gaseous material on a 10,000 au scale in which a prominent outflow cavity is carved. Within the central ~700 au, the circumstellar matter forms a flattened pseudo-disk where material is infalling with conserved angular momentum. Within ~350 au, the velocity profile is more consistent with a disk in Keplerian rotation around a central star of 0.1 M_Sun. We determined an infall rate from the envelope onto the disk of 6 x 10^-6 M_Sun/yr, a factor of a few higher than the quiescent accretion rate from the disk onto the star, hinting at a mismatch between the infall and accretion rates as the cause of the eruption.

Understanding the complex chemistry of solar-type protostars

Calcutt, Hannah

Complex organic molecules have been detected in every environment associated with star formation. Their detection is critical to understanding the chemical development of star-forming regions, as well as exploring the link between the early stages of star formation and the formation of Solar System bodies. Of particular interest to such studies is the detection of complex organic molecules containing nitrogen, owing to the significance nitrogen plays in the formation of life. Abundances of complex nitrogen-bearing organics have also been observed to vary significantly in different star forming regions, with this chemical differentiation even suggested as a tracer of protostellar evolution. With uncertain formation routes, however, and differing physical conditions between sources, the exact origin of this differentiation remains unclear. In this work, we present results from a survey of complex nitrogen-bearing organics towards the low-mass protostellar binary IRAS 16293-2422. We use ALMA observations from the Protostellar Interferometric Line Survey (PILS), to study nitrogen chemistry at an unprecedented spectral and spatial resolution in this source. We will present the key constraints this survey has placed on the formation routes for a number of molecules in this source, as well as constraints on luminosity, physical structure, and evolution. 

Constraining the stellar energetic particle flux in young solar-like stars

Rab, Christian

High energy ionization sources such as X-rays, cosmic rays and stellar energetic particles (stellar cosmic rays, SP) can ionize molecular hydrogen, the most abundant chemical species in the environment of young stars. Therefore, they play a crucial role in the chemistry and evolution of the circumstellar environment. Energetic particles are likely the reason for the abundance anomalies of short-lived radionuclides measured in meteoritic material. However, it is still unclear if those anomalies are a consequence of enhanced irradiation by cosmic rays (e.g. nearby supernovae) or enhanced irradiation by stellar energetic particles in the early stages of the solar system formation. We present models which allow for studying the impact of SP on the chemistry of the circumstellar material of young solar-like stars and the observability of this interaction.We use the radiation thermo-chemical disk code ProDiMo (PROtoplanetary DIsk MOdel) to model the impact of those high-energy ionization sources on the chemistry of planet-forming disks. The model includes X-ray radiative transfer and makes use of particle transport models to calculate the individual molecular hydrogen ionization rates in the disk. We study the impact on the chemistry via the ionization tracers HCO+ and N2H+. We argue that spatially resolved observations of those molecules combined with detailed models allow for disentangling the contribution of the individual high-energy ionization sources and to put constraints on the SP flux in T Tauri stars.We further present a new extension to ProDiMo, which allows modelling of the disk plus envelope structure of embedded stars (i.e. Class I). Recent observations indicate that enhanced stellar particle irradiation might already happen in those early phases of the star and planet formation process. We present first results of our self-consistent high energy ionization models for this early stages and discuss possible constraints for this scenario.

Resolving the origin of the hydrogen line emission in YSOs with near-infrared interferometry

Kreplin, Alexander

Jets and out?ows play a fundamental role in star formation and the physics of the accretion-ejection process. While the hot circumstellar dust can be studied in the near-infrared continuum, hot ionised gas can be studied in lines, in particular, the Br? line. The unprecedented milliarcsecond resolution achievable with the Very Large Telescope Interferometer (VLTI) allows us to study the origin of the line emission and kinematics of the physical processes involved in the creation of these lines, e.g., magnetospheric accretion or disk wind. In this talk, we show the application of various modelling techniques ranging from geometric models to state-of-the art disk wind radiative transfer codes on Herbig Ae/Be stars observed with the VLTI/AMBER and GRAVITY instruments. In the high mass protobinary system IRAS17216-3801 we demonstrate how spectro-interferometric observations of the Br? and CO lines can be used to estimate the fractional contribution to the line emission of hot (10^4 K) and warm (10^3 K) gas of each star within a young binary system. Near-Infrared interferometric observations of the Herbig Ae/Be star MWC120 reveal that the source of Br? emission in this system seems to be dominated by a disk wind rather than, e.g., by magnetospheric accretion. Our study on the Herbig B[e] star MWC 297 combines VLTI/AMBER high-spectral dispersion interferometry (R=12,000) and CRIRES spectro-astrometry (R=100,000). Using aperture synthesis imaging techniques, we reconstruct velocity-resolved channel maps and moment maps that reveal the motion of the Br?-emitting gas in six velocity channels, marking the first time that kinematic effects in the sub-AU inner regions of a protoplanetary disk could be directly imaged. We model all observables using a kinematic model that includes a Keplerian-rotating velocity component as well as outflowing velocity component, as inspired by a magneto-centrifugal disk-wind scenario.


Freire da Silva, Danielly

 Debris discs are commonly detected orbiting main-sequence stars, but little is known regarding their fate as stars evolve along the subgiant and giant stages. Nevertheless, the literature reports a few studies show strong evidence on the presence of mid-IR excess in G and K stars of luminosity class III, using photometric data from the Two-Micron All-Sky Survey (2MASS) and GLIMPSE catalogues and, more recently from WISE space borne. While the origin of these excesses remains uncertain, it is plausible that they arise from debris discs around these stars. The present study brings an unprecedented survey in the search for mid-IR excess among single and binary F, G and K-type evolved stars of luminosity classes IV, III, II and Ib.  For this study, we use WISE and 2MASS photometric data for a sample of 3000 evolved stars, complete up to visual magnitude of 6.5. As major results, we found that the frequency of evolved stars showing mid-IR WISE excess increases from the luminosity classes IV and III to luminosity classes II and Ib. In addition, there is no clear difference between the presence of IR excess in binary and single stars for all the analyzed luminosity classes.

Chemical Tracers in Proto-Brown Dwarfs – Observations and Modelling

Riaz, Basmah

Brown dwarfs bridge the gap between Solar-type stars and giant planets and share characteristics with both. This makes them interesting cases to study the analogies in the early formation and evolutionary stages with the proto-Suns and proto-planets. We have conducted the first substantial molecular line survey to study the chemistry in early-stage Class 0/I proto-brown dwarfs. Observations with the IRAM 30m telescope have confirmed detection in 16 molecular species. We have derived self-consistent physical+chemical models that can reproduce the observed molecular line emission and provide a first-order approximation to the internal structure of the proto-brown dwarfs. Results indicate that the species HCN, CS, DCO+, DCN, and N2D+ can trace the high-density emission towards the inner protoplanetary disk and can reveal the small-scale structures in the proto-brown dwarfs, whereas the HCO+, HNC, and CO molecules are severely depleted from the gas phase in the inner, dense regions. We find an enhanced abundance for HNC compared to HCN, which suggests that the chemistry of the nitrogen-bearing species is dominated by kinetic temperature gradients. The molecular abundances for the proto-brown dwarfs have been compared with Class 0/I protostars, covering a range of ~0.1 – 20 Lsun in the bolometric luminosities. We find a decline in the HCO+, HCN, and H2CO abundances with decreasing luminosities, while the species CS, CO, HNC, and CN are nearly constant and show no particular trend with the bolometric luminosity. There is a large spread of ~2 orders of magnitude in the molecular abundances for the proto-brown dwarfs, which reflects the source to source variations in their chemical composition and internal structure. We will discuss the similarities in the chemical structure of the proto-brown dwarfs with pre-stellar cores, protostars, and proto-planets, and the development of our physical+chemical models to understand the chemical evolution in proto-brown dwarfs.

Revealing a gap in the protoplanetary disk of DI Cha A with mid-infrared interferometry

Gerják, Tímea

DI Cha A is the brightest component of a quadruple stellar system in the Chamaeleon star forming region.  It is a G2-type T Tauri star at a distance of 200 pc, possessing a circumstellar disk.We studied the structure of the disk using archival high spatial resolution mid-infrared interferometric observations obtained with the VLTI/MIDI instrument, and also multi-wavelength photometric data. We applied radiative transfer modeling with the RADMC-3D software package using a two-component model, which contains a halo and a disk component. We found that the inner radius of the mid-infrared emitting disk is 1.5 au, far larger than the dust sublimation radius, indicating the presence of a gap. For the halo the best fitting outer radius is 0.4 au.From this we conclude that the disk of DI Cha A can be classified as a (pre-)transitional disk, possibly indicating ongoing planet formation within.

Dust evolution in the circumstellar disk of the unclassified B[e] star HD 50138

Gerják, Tímea

We have studied the disk of the unclassified B[e] star, HD 50138, in order to find indications for the evolutionary status of the object (whether it is a young Herbig object or a main-sequence star).Using high spatial resolution 8-13 µm interferometric measurements by VLTI/MIDI we analyzed the size, time-variability and the 10 µm silicate feature.By fitting simple disk models, we determined the inclination and mid-IR size of the disk, thus confirming the former result from less observations. We analyzed the mid-IR temporal variability of different regions of the disk, and concluded that it is not experiencing significant changes over time.We also studied the mid-IR silicate feature, by determining the feature amplitude and the 11.3/9.8 µm flux ratio. The latter parameter is a good indicator of the grain size and crystallinity. The shape of the feature suggests the presence of crystalline silicate grains. We found that the inner disk spectra show weaker silicate feature with larger 11.3/9.8 µm flux ratio compared to the outer disk spectra, indicating larger dust grains in the inner disk. This can be caused by dust evolution, which is also observed in a number of pre-main sequence systems.

Elongations in Sco-Cen with Gaia DR2

Larreina, Irati

Bouy & Alves (2015) studied the overdensities of massive blue stars in the solar neighbourhood. Using distances for OB stars from the Hipparcos catalogue they identified three large-scale structures, named "blue streams". Confirmation of their results can be crucial to understand the star formation history in many important star forming regions, such as Orion and Sco-Cen.Our interest lies in the study of large-scale structures on the solar vicinity. Using the Tycho-Gaia astrometric solution (TGAS) from GAIA DR1 we created a 3D Kernel Density Estimation (KDE) map. The overdensities on this map correspond mainly to well known clusters and associations of various ages. This was implemented using an Epanechnicov kernel with a bandwidth of 12 pc and error cuts for the parallax and proper motion in RA and Dec < 20%. We also filtered the sample by parallax > 5 (200pc) and B-V < 0.5. Due to the errors in parallax many structures appear elongated towards the Sun, except for the Sco-Cen association (Upper Sco, UCL and LCC), meaning that the elongations in this association might be real. A smaller cluster candidate was found previously categorised as part of UCL and recently studied by Röser et al. (2017) around V1062 Sco. We observe a very prominent gap between UCL and LCC unnoticed before, probably caused by a lower stellar density in the region or the incompleteness of OB stars in the catalogue. We also notice some substructures on Upper Sco and LCC which need further study. We will show the implemented results of these structures using Gaia DR2, available in April. These results will be important to throw light on the star formation history of this association and ultimately test the existence of blue streams.

Prestellar Core Collisions

Herbst-Kiss, Gabor

I will present simulations of prestellar core collisions using the smoothed particle hydrodynamics code GANDALF. We focus on changes of the angular momentum, the internal energy, and the mass before and after the collision of prestellar cores in the interstellar medium. In the timeline of star formation, a molecular cloud has to lose 6-7 orders of magnitude of its initial specific angular momentum to the final formed protostar. This loss happens in distinct stages due to certain processes (e.g. magnetic braking, fragmentation and turbulence). The first entities formed out of fragmenting filaments are structures of several Jeans masses. These objects with small seperation could collide in regions of high core density. Also colliding clouds and filaments were already identified (e.g. in the Pipe Nebula) which favor collision processes. To study the effects of these collisions on the loss of angular momentum, we use Bonnor-Ebert and truncated Plummer spheres in a variety of initial states. Therefore, a set of simulations with various initial seperation distances, masses, impact parameters, alignments of rotation axis and turbulence will be run. We analyze the transport of angular momentum during the collision and loss due to linear movement and dissipation resulting from the collision. The numerical study of collision scenarios presents the conditions set to form stable, virially bound and unbound objects and the initiation for collapse of prestellar cores. The resulting v_lsr gradient of the 2D projected core, the oscillation patterns and dissipated material after the merge will help in the identification and interpretation of real observed cores. We will show preliminary results on our first targets of cores in the Pipe Nebula.

The effect of photoevaporation on the formation of planets in the habitable zone

Császár, Anna

An important research topic in astrophysics, which has a special interest not only for the scientificcommunity but also for all, is whether life may have evolved in some exoplanetary systems. The region of a planetary system, where water-based life could appear is called the habitable zone.In order to understand and numerically simulate planet formation one should investigate the time-evolution of protoplanetary disks being governed by gas accretion onto the star and photo-evaporation by the radiation of the central star. Using a 1D time evolving disk model (Lynden-Bell & Pringle, 1974, MNRAS 168, 603) we implement the formulae for X-ray photoevaporation provided by Owen et al. (2012, MNRAS 424, 1880). Beside the gravitational interactions between planets, planetary systems obtain their final orbital configuration by migration in the gas disk. Therefore we calculated the timescales for orbital decay, as well as the damping timescales for eccentricities and inclinations using the local physical parameters of the protoplanetary disks obtained during numerical simulations.Since a gap is forming in the disk as a result of photoevaporation, we particularly investigate its effect on the dynamical behavior of planets. This may have consequences as accummulating terrestrial planets in the habitable zone around the star, if the location of the gap overlaps with the habitable zone. One of the major goals of our research is to map the extent of this overlapping.

Tracing the early planet formation with molecular lines: chemo-dynamical simulations of vortex structures in protoplanetary disks.

Dzyurkevich, Natalia

The infraread observations of dust in protoplanetary disks show us spectacular structures like numerous gaps, vortices and spirals. In order to explain those, both the planet formation and the planet presence are considered. Molecular lines provide information about disks that is complementary to dust continuum observations.We use a reduced chemical network containing main carbon- and sulfur-bearing species to find the molecular species which can be sensitive to the presence of vortex in the protoplanetary disk. We merge the reduced chemical network and state-of-the-art radiative hydrodinamical code to perform the chemo-dynamical simulations of planet-bearing and planet-forming sites.

Investigating Transient Events in Active Stars

Alvarado Gomez, Julian David

Stellar magnetic fields completely dominate the environment around late-type stars. They are responsible for driving the coronal high-energy radiation (e.g. EUV/X-rays), the development of stellar winds, and the generation of transient events such as flares and coronal mass ejections (CMEs). While considerable progress has been made for the first two processes, our understanding of the eruptive behavior of active stars is still very limited. This information is critical as these phenomena can have a strong or even catastrophic impact on planetary systems. This is of particular importance during the early stages of evolution where they can become the dominant factor in determining the physical properties around late-type stars. In this context, I will present the initial results of a joint observational and numerical project, aimed at studying the properties of eruptive phenomena in active stars. The first aspect comprises the analysis of simultaneous observations of X-ray and white light flares of young stars, acquired with the Chandra and Kepler (K2) telescopes. On the numerical side, I will present detailed 3D MHD simulations of CMEs in active stars, developed using one of the latest models employed for space weather forecasting in the solar system. These results will be discussed in the general solar-stellar context, taking into account the observed properties of the magnetic fields in which they develop.

Evolution of multiplanet systems in 2D and 3D radiative disks

Chrenko, Ondrej

Dynamical evolution of an isolated low-mass protoplanet is driven by gravitational interactions with its natal protoplanetary disk. Proper migration modelling requires radiative hydrodynamics (RHD) in order to correctly account for the disk thermodynamics (e.g. Kley et al. 2009) and advection-diffusion phenomena occurring close to the protoplanet (e.g. Lega et al. 2014, Benitez-Llambay et al. 2015). However, only a limited number of RHD models involving multiple Earth-like (or even smaller) protoplanets have been constructed up to date.Here we study the evolution of such a multiplanet system within a radiative disk. First, we review the results of Chrenko et al. (2017), highlighting the importance of so-called hot-trail effect related (in this particular case) to the heating of protoplanets by pebble accretion. Specifically, we demonstrate how the hot-trail effect excites orbital eccentricities, increases frequency of close encounters, prevents resonant captures and allows for merging of protoplanets. The simulations are obtained using the 2D Fargo_Thorin code, and thus contain several inevitable caveats: The damping of orbital inclinations is not self-consistent but prescribed, the hot-trail does not affect inclinations, and vertical averaging fails to fully reproduce the flows in the vicinity of a protoplanet.We therefore present additional simulations in 3D using the Fargo3D code (Benitez-Llambay & Masset 2016) into which we implemented a solver of the radiation-gas energy equations (similar to Bitsch et al. 2013) and also the Rebound/IAS15 integrator (Rein & Spiegel 2015), capable of resolving close encounters and possible merging of protoplanets. We compare the results with the above-mentioned 2D modelling and discuss the differences. Additionally, the model is applied to the inner part of the disk in order to compare the properties of the synthetic systems with the observed close-in exoplanets.

Multiplicity Among Young Stellar Objects in Orion A

Ackerl, Christine

The initial multiplicity properties of stars carry the footprints of the mechanisms involved in their formation. Additionally, multiplicity also plays an important role in planet formation or even habitability. It is therefore inevitable to study under which circumstances stars form alone or in multiples and how their separations evolve over time. While multiplicity among main sequence stars is already well established (e.g. Duquennoy & Mayor 1991) this is not the case for young stellar objects. Studies concentrating on young binaries are mostly carried out for relatively small populations and in very distinct environments, for that reason, the results are ambivalent and leave unanswered questions. For example, whether and how does initial stellar multiplicity depend on environmental conditions? In order to provide a more complete picture, a statistically significant sample of young binaries that covers an entire star forming region with diverse physical conditions is needed. Using the Vienna Survey in Orion (Meingast et al. 2016) we are able to present the largest known sample of young visual binaries towards one single star forming cloud, the rich and nearby star forming region Orion A. The survey provides high-quality seeing limited ESO-VISTA images and JHKs-photometry for ~800,000 sources and covers a vast range of different star forming environments, from well known dense clusters to isolated (Taurus-like) environments towards the southern end of Orion A. Our sample is sensitive to separations > 300 AU and is about an order of magnitude larger when compared to previous studies in this region (e.g. Kounkel et al. 2016).

Infrared Variability of Young Stars

Wolk, Scott

One of the recent changes to our understanding of young stars is the realization of how dynamic these systems are in the infrared. I present time series data from the CFHT and Spitzer observatories. We have monitored  thousands of young stars down to J˜ 20 using the WFCAM and [4.5] ~ 13 using Spitzer/IRAC. Most of the young stars with disks are significantly variable. By studying variability in young stellar objects (YSOs) in the H - K, K color-magnitude diagram, we are able to distinguish among  physical mechanisms of variability. Many variables show color behavior indicating either dust-extinction or disk/accretion charges. At the Spitzer wavelengths, more than 80% of the Class I, flat spectrum, and Class II sources are found to vary. The amplitude of the variability is larger in more embedded YSOs. Most of the Class I/II objects exhibit redder colors in a fainter state, which is compatible with time-variable extinction. A few become bluer when fainter, which may be explained by significant changes in the structure of the inner disk. 

Early Evolution of Icy Planetesimals: How Much Volatiles and Organics Are Lost Prior to Planetary Interactions?

Sarid, Gal

Early thermal and structural processes that affect planetesimals have strong implications for planet formation scenarios and the attributes of large dusty aggregates in proto-planetary disks. Observations and models of our solar system's planetary bodies have shown that outer nebula material has mixed with the inner parts of the solar disk, at various stages. The extent of this mixing is not entirely clear, but has been suggested to affect both atmosphere and surface compositions. Analogues processes may occur around other stars.  We focus here on a less-studied epoch, between natal disk and planet evolution, in which small planetesimals form in the outer parts of a planetary disk and experience early bulk processing. We model the evolution of small icy planetesimals (up to ~10 km), such that radioactive heating, melting and convection play a negligible role, at most. Our starting point will rely on canonical comet models, which will then vary by: stellar radiation flux (affecting the major source of energy input), orbital lifetimes (derived from dynamical stability calculations), gas disk lifetimes (affecting surface pressure, material ablation and volatile loss rates), sizes (affecting heating/cooling timescales), initial porosity values (affecting heat and mass transfer) and composition ratios (water relative to silicate and volatile species relative to water). Emphasis is put on the emerging mechanical strength, heat input history, amorphous-to-crystalline water ice transition, and potential retention of volatile and organic species. At the end stage, whatever is not incorporated in planetary building blocks has little chance of being incorporated into the planets themselves.The varied thermal histories impose an additional composition gradient to that inherited from the disk’s physical-chemical state.Our framing question is: How much icy and volatile material is out there to be delivered to the atmospheres and surfaces of terrestrial planets?

The NASA Exoplanet Exploration Program: Update and Prospects for the 2020's and Beyond

Mamajek, Eric

The NASA Exoplanet Exploration Program (ExEP) is responsible forimplementing NASA's plans for discovering and characterizingexoplanets, and identifying candidates that could harbor life.  ExEPmanages concept studies, technology development programs, ground-basedscience programs that help complete the science goals of current andfuture NASA missions (and that enable the design of next generationexoplanet missions), and communicates the excitement of exoplanetresearch to the public.  We will review recent activities in theNASA-NSF exoplanet research collaboration (NN-Explore), progress inthe characterization of exozodiacal light, the status of ongoingstudies of future exoplanet flagship missions, and recent technologymilestones (including updates on the progress of starshade andcoronagraph technology capable of imaging and characterizingexo-Earths).

Galactic context to local star formation: the local neighborhood in the Gaia era

Alves, Joao

Gaia will revolutionize our view of the local galactic neighborhood not only for the precise measurements of its stellar content but also for the exquisite 3D view of the local ISM. In this contribution, I will focus on the interplay between local massive stars and molecular cloud complexes (d < 500 pc) where resolved star formation can be studied, from dense core formation to circumstellar disk dissipation. We will start by describing the newly discovered Blue Streams, their validation from ground-based spectroscopic data and Gaia data, and how these streams are impacting the structure of both the diffuse and dense star-forming ISM. We will present Herschel maps of the nearby complexes and show evidence that stellar feedback from the streams plays a fundamental role not only in assembling but also shaping filaments and cores, as well as driving most of the observed turbulence. We will argue that the Blue Streams, because of their massive star content proximity to Earth, can have an impact on life on the planet. I will end by pointing to a large NIR survey of the local complexes carried out in Vienna (VISIONS that together with Gaia data will allow for the first 3D space motion map of the local star-forming ISM, opening a new window on ISM dynamics.  

The search for precursors of Solar System alikes in a high-mass star forming area

Bogner, Rebeka

Recent theories on the formation of the Solar System turned the attention to the study of low mass cloud cores in massive star forming regions. The Herschel satellite with its wavelength coverage could detect massive young stellar objects at all evolutionary stages and was able to detect the precursors of O and B stars. The Rosette Molecular Cloud (RMC) at 1.6 kpc from the Sun is a well-known area: the OB cluster NGC 2244 at the centre is blowing a cavity into it, resulting in an expanding HII region interacting with a high-mass star forming molecular cloud which has a highly filamentary structure with dense cores having a wide range of masses. These prestellar and protostellar cores were observed by Herschel and key core properties such as bolometric luminosity and mass were derived from its data. With the Effelsberg 100m telescope a sample of these cores - between 3-40 solar masses - were observed in NH3 (1,1) and (2,2) inversion lines. Ammonia is invaluable in deriving physical parameters of the dense gas such as gas temperature and optical depth, along with revealing the temperature structure it makes the study of core stability possible which are our aims to examine. Compared with Herschel measurements the differences between the dust and gas properties can be investigated. As the origins and evolution of low-mass stars in high-mass star forming environments is still unclear, with our selection of cores we are planning to gain insight - by searching for smaller fragments of cores and examining their properties - on the conditions in which low-mass stars can form in an environment dominated by the effects and feedback of massive star formation - as our Solar System might have originated from such a violent environment.

Characterizing the Obliquity Variability of Terrestrial Habitable Zone Planets

Shan, Yutong

Obliquity variations could play an important role in the climate evolution and habitability of a planet. Orbital modulations caused by planetary companions and the planetary spin axis precession due to the torque from the host star may lead to resonant interactions and cause large amplitude obliquity variability. We discuss the spin-axis dynamics of terrestrial planets in multi-planet systems, using two specific habitable zone exoplanets, Kepler-62f and Kepler-186f, for illustration. Using numerical and analytical techniques, we characterize regions in parameter space where their obliquities are variable. We find that the locations of variability in lower obliquity regimes (?40 deg) are fine-tuned over the planetary properties and system architecture. As an example, if rotating at 24h, the obliquities of both Kepler-62f and Kepler-186f are stable below -40 deg, whereas the high obliquity regions (?60 deg) allow moderate variabilities. However, for other rotation periods, the lower obliquity regions could allow large-amplitude oscillations. We show how extra undetected planetary companions and/or the existence of a satellite could also destabilize obliquity at various values. Even small deviation from coplanar configurations could greatly amplify variability. Our analytical results has implications for characterizing obliquity evolution, and in turn climate stability, as a consideration for habitability.

Assessing the NUV variability of stars across the spectral sequence

Bertone, Emanuele

Intensity and variability of the stellar ultraviolet radiation is one of the main variables that affect the space weather of planets and determine their conditions of habitability.We present a thourough study of the variability of stars of all spectral types in the near ultraviolet band (NUV), by using data from the GALEX-CAUSE survey of the Kepler field.The whole Kepler field was observed in the NUV band (1771-2931 angstrom), during 46 days in 2012 AugustSeptember, using 300 GALEX orbits, funded by Cornell University  (PI J. Lloyd). We constructed a large photometric catalog of light curves of more than 400,000 stars of all spectral types, that we used to determine the flux variability as a function of spectral type.Through the use of diagnostic diagrams we are also able to characterize the kind of variability of these objects. Preliminary results indicates a median NUV flux variability of 11% for solar analogs.

The Secular Evolution of the Sun's Rotation and the Solar Energetic Photon and Particle Radiation Environment

Drake, Jeremy

Recent years have witnessed a growing realisation that energetic photon and particle radiation plays a crucial role in the formation and evolution of planets, and possibly in the origin of life itself.  The Sun's energetic radiation output has decreased by several orders of magnitude since its beginning as a T Tauri star. The radiation environment through time is determined by the Sun's magnetic activity, which in turn both depends on and controls its rotation rate. Here, we show how new insights into stellar magnetic field morphology lead to a new predictive model of stellar winds and rotation evolution that matches observed rotation rates of Sun-like stars of all ages and allows us to determine the energetic photon and particle radiation of the Sun and stars through history.

Iron-nickel distribution on experimental barred olivine-like chondrules

Hernández-Reséndiz, Patricia

Barred olivine chondrules (BO) are fully melted chondrules and they constitute less than 10% of chondrules in ordinary chondrites (Jones 2012). We have prepared in our laboratory experimental BO chondrule-like melts with the purpose of studying the formation processes of type IA BO chondrules, as well as their physical and chemical characteristics. Samples were melted with the help of a 50W CO2 laser emitting in the infrared at a wavelength of 10.6µm inside a vacuum chamber at 0.76atm. We measured the distribution of relevant elements present in chondrules in our experimental samples (Fe, Mg, Ni and Mn), in order to understand the origin of chemical zoning and the evaporation rates of Fe and Ni. The values obtained for the Fe coefficient suggest that the crystallization occurred after a significant amount of evaporation of FeO (~50% of the total FeO content for starting material). We highlight Fe-Ni particles present in our analogs, with a similar composition as reported inside chondrules of Semarkona LL3.0 chondrite, and explore the hypothesis that Fe-Ni grains may have formed at the melting stage of chondrule formation. If this hypothesis is valid, Fe-Ni abundances in metal grains inside natural chondrules can yield information about pressure, evaporation and cooling rates during chondrule formation.

Formation and Galactic Dynamic Evolution of Young Star Clusters

Hetem, Annibal

We present an analysis of a sample of clusters of young stars in order to investigate the inherent properties of clustering and dynamic evolution of stellar components. In previous works, we measured the parameter Q for a set of 25 clusters and the results were correlated with other properties of the spatial distributions determined through the King profile and show that almost half of these groups have a relation with the fractal dimension of their parental cloud. The statistical parameter Q was measured for the clusters and its correlations with the estimated fractal dimension for the projected near clouds are presented. There are also indications of the presence of substructures similar to those observed in the surrounding clouds. However, other clusters have a radial distribution that does not coincide with the structure of the clouds. These properties may lead to conclusions about the initial conditions of clusters formation (cold collapse or hot collapse), initial evolution (bound or not) and its expected galactic dynamic evolution (crossing time). These studies may give us information about the history of the influence of the Galaxy on clusters and how they were affected by their passage through their structures. In addition, present the application of new mathematical and numerical techniques with potentiality for use in models of filamentary structures.

Probing the physical conditions surrounding young star clusters: inferences from features of molecular, atomic and ionized species

Gregorio-Hetem, Jane

The scenario of star clusters formation can be better understood based on the detailed study of the dynamical conditions of the associated gas, clustering properties and effects of ionizing sources, among others. Our previous works revealed an exotic environment surrounding several young stellar groups. A study of fractal statistics of young clusters showed the stars distributed in filamentary sub-structures that were probably formed under supervirial conditions and feedback from massive stars (ionization, winds). The answer for questions raised from our previous results depends on the comparison among the distributions of molecular, atomic and ionized gas for a large sample of objects, which are investigated here by means of optical and infrared observations obtained with the SOAR and T80S telescopes for a selected sample of star clusters and associations. These observations provided a complete catalog with multiband photometric data for the members of the studied star-forming regions and clusters that were characterized according to the color-color diagrams and fluxes ratios, which are indicators of accretion rate, magnetic activity and the physical conditions of the nebular emission.

Dynamical environments of MU69: a state of chaotic clearing

Shevchenko, Ivan

The second (after Pluto) plausible target object for the New Horizons mission is 2014 MU69. It is a classical TNO, a primordial contact binary. Identifying any material in the vicinities of a target object is of on especial concern for planning cosmic fly-byes, as it is hazardous for a space probe. Luckily, no such material has been reported for MU69 up to now. The point of our report is that this lucky absence is just a dynamical consequence of the physical nature of MU69. Spinning gravitating dumbbells create zones of dynamical chaos around them, and this has a clearing effect: any material put in orbits around a rotating dumbbell (e.g., any material ejected from its surface) cannot be long-lived in such zones; it either escapes into space, or returns to the parent body's surface. As the orbiting matter is removed in this way, a spinning gravitating dumbbell clears its vicinities. We show that MU69 is able to create such a clearing, making itself a safe and hospitable target for a space mission. Therefore, the guest probe is expected to be safe on arrival.

Resonant multi-lane patterns in circumbinary young debris disks

Shevchenko, Ivan

Formation of resonant multi-lane patterns in circumbinary young debris disks with planets is considered in a set of representative massively simulated models. We find that the long-term-stable resonant patterns are generically formed, shepherded by embedded planets. The patterns are multi-lane, i.e., they consist of several concentric rings. Statistical dependences of their parameters on the planetary orbital parameters are recovered. Relevant additional massive simulations of planetesimal disks in systems with parameters of Kepler-16, Kepler-34, and Kepler-35 are accomplished and described. We find that the co-orbital patterns generically form in systems with moderate orbital eccentricities of the binary's and planetary orbits (like in Kepler-16 and 35 cases). We argue that any observational identification of characteristic resonant ring-like patterns in disks of the considered class may betray presence of planets shepherding the patterns.

Heating mechanisms in accretion disks around young stellar objects

Jatenco-Pereira, Vera

Accretion disks are observed around young stellar objects such as T Tauri stars. In order to complete the star formation, particles in the disk need to loose angular momentum in order to be accreted into the central object. The magneto-rotational instability (MRI) is probably the mechanism responsible for a magneto-hydrodynamic (MHD) turbulence that leads to disk accretion, which implies the disk particles to be coupled with the magnetic filed lines. As the temperatures of the particles in the disk are low, the ionization rates are also very small. In order to increase the disk temperature, besides the viscous heating mechanism often included in the models by means of the alpha-prescription, we study the damping of magneto-acoustic waves and the damping mechanisms of Alfvén waves, the turbulent and non-linear, as an additional heating source. We show that these damping mechanisms can increase the ionization fraction, making possible the presence of the MRI in a large part of the disk. In particular, the mechanism derived that couples the turbulent and non-linear damping mechanisms of Alfvén waves proved to be very efficient, generating temperatures almost one order of magnitude higher than those mechanisms considered independently.

A Hydrodynamic Modeling of Atmospheric Escape and Absorption Line of WASP-12b

Dwivedi, Navin Kumar

A systematic and self-consistent modeling of stellar wind (SW) interaction with upper atmosphere of WASP-12b exoplanet has been performed. We assume that the planet is weakly magnetized and therefore the intrinsic planetary magnetic field is not considered in the model.  The model includes the basic hydrogen chemistry and describes the expansion of the planetary upper atmosphere and mass loss due to stellar XUV radiative heating. The interaction of the escaping planetary wind with the background plasmas is also included. The two case-scenarios of the planetary material escape and interaction with the SW have been modeled for different XUV radiations and SW parameters, namely the case with formation of a shock (without the inclusion of tidal force) and the stream formation case (with the account of tidal force). The obtained results show that in case of slow SW and without an account of the tidal force, a shock is formed around the planet because of its high orbital velocity, which dominates in the background plasma speed. In this case, the planetary mass loss is controlled completely by the stellar radiation flux. In the second case, the mass loss is mainly due to the gravitational interaction effects. The dynamics of MgII ions was modeled with three different sets of SW parameters and XUV flux values under a realistic Sun-like star condition. The results appear in good agreement with the observations, but do not reveal any signature of early ingress.

The XUV Sun in Time*

Nemec, Nina-Elisabeth

The evolution of the X-ray and extreme ultraviolet radiation (XUV) of a star is important to understand the evolution of planetary atmospheres as this radiation heats and ionizes the upper layers of such atmospheres. The XUV output of solar-type stars varies on evolutionary timescales, showing a gradual decline seen at all wavelength regimes. However, the XUV radiation is essentially unobservable for most stars between  approximately 10 and 92 nm because of interstellar absorption due to hydrogen.We present a novel method based on the stellar S-index or R’HK (probing the strength of the Ca II H and K lines), using calculated spectra of elementary solar features and their filling factors to model the stellar flux across the XUV wavelength range. We present filling factor relations for up to eight different solar features that are extrapolated to stars at much higher activity levels with the help of some filling factor information (in particular spots) from stars. We then synthesize the full spectra for any given stellar activity level. The method can be extended to non-solar spectral types.  * dedicated to the late Juan Fontenla, who provided the elementary, calculated spectra of the solar features

Herschel observations of the HH211 protostellar system

Dionatos, Odysseas

The birth of Sun-like stars is a complex process where several physical processes are involved but whose respective roles are not yet clear. On the one hand, the young stellar object accretes matter from a collapsing envelope. The gravitational energy released in the process heats up the material surrounding the protostar, creating warm regions enriched in complex organic molecules. On the other hand, the presence of angular momentum and magnetic fields leads to the formation of circumstellar disks and the ejection of matter, in the form of collimated jets and wide-angle outflows. In the time-domain, accretion is most likely episodic causing sudden increases in the luminosity of the system and providing, along with the ejecta, energetic feedback to the system.Mid- and far-infrared observations of the environment around embedded protostars reveal a plethora of high excitation molecular and atomic emission lines. A number of different mechanisms for the origin of these lines have been proposed, including shocks induced by protostellar jets and radiation by the embedded protostar interacting with its immediate surroundings. We will report on one of the most dramatic cases, the HH211 protostellar system, where all processes can be seen in action. Due to its pristine appearance, HH 211 stands out amongst the youngest, best-studied outflows which has made it become a text-book example. Being very young and relatively compact (estimated dynamical timescales are less than 500 yr), it has a rather simple and well-defined geometry consisting of a central young stellar object, nearly symmetric outflows and two bright terminal shocks at the opposite outflow ends. Despite the apparent symmetry, analysis of Herschel spectral-line mapping observations demonstrates that the emission around the source and the two terminal bowshocks is dominated by diverse processes that will be detailed in our presentation.

Toward understanding origin of gas in debris disks

Higuchi, Aya

Debris disks have optically thin dust components around main-sequence stars. We reduced ALMA archival data of the debris disk candidates and derived the dust and gas mass assuming the ISM abundance of CO/H2=10-4. From the result, we found a good correlation between dust mass and age of the central star: dust masses decrease with age of central stars. We expected the similar trend that gas masses decrease with the age, but found no trend between them. We thus concluded the ISM abundance is not a good assumption to derive H2 mass for debris disks. In addition, recently, we have firstly detected [C I] emissions in the gaseous debris disks of 49Ceti and ßPictoris with the ASTE. If C/CO ratio can be obtained by observations, there is a possibility to estimate the amount of H2 using the chemical reaction of CO.

Planetesimal Formation at the Dead-zone Inner Boundary and Its Observational Signatures

UEDA, Takahiro

The inner region of protoplanetary disks is the birthplace of rocky planetesimals and planets. One preferential site of rocky planetesimal formation is the inner edge of the dead zone. Across the dead-zone inner edge, the turbulent viscosity arising from magneto-rotational instability steeply decreases from inside out, resulting in a local maximum in the radial profile of the gas pressure. The pressure maximum traps solid particles and the local dust-to-gas mass ratio increases, leading to rocky planetesimal formation via the streaming instability.We performed simulations of dust and gas disk evolution with a broad range of the critical fragmentation velocity of silicate dust and the strength of turbulence in order to investigate the dust-pileup at the dead-zone inner boundary. Around the dead-zone inner boundary, dust particles are easy to fragment into small particles because of its high temperature, which interferes with the dust-pileup. We derived criteria for the dust-pileup as a function of the critical fragmentation velocity and the strength of turbulence, and found that if the critical fragmentation velocity is 1 m/s, the classical alpha value for turbulent strenght in the dead-zone should be lower than 0.0003 to operate the dust-pileup. Using the dust distribution obtained above, we also performed the radiative transfer simulations with RADMC3D to construct a model of the inner region of protoplanetary disks including the effect of the dust-pileup. We found that if dust particles strongly concentrate on the dead-zone inner boundary, the dust-pileup acts as a optically thick dust wall which could be observed as a bright ring next to the bright ring of the inner rim of the dust disk. And also, this dust wall casts a shadow behind the dead-zone inner boundary, which can be extended up to 10 au. These characteristic structures could be tracers of the dust-pileup operating the planetesimal formation.

Dust trapping and coagulation in protoplanetary disks

Li, Yaping

Grain growth from the submircro-size, typical size of dust from the ISM, to millimeter (mm) and centimeter sizes is the first step toward the formation of planet inside protoplanetary disks (PPDs). However, such process is still poorly understood because of the complex dust/gas dynamical process in disks. In this work, we carry out two-fluid (gas+dust) hydrodynamical simulations to study the dust coagulation processes in PPDs. By a systematic comparison with the continuum emission at several mm bands from ALMA observations,  we find that ringed structures are predicated in the unresolved disks for those with mm spectral indexes as low as 2. With the help of ringed structures to slow down the dust radial drift and speed up the dust growth, both a high fragmentation velocity and a high dust surface density can produce such a shallow spectral slope. Future high resolution ALMA observations of these low spectral index sources can be used to test the existence of the ringed structures in the inner region of the disk and to further constrain the fragmentation velocity, one key parameter of the dust coagulation model. The physical implications of the expected rings are briefly discussed in terms of the planet formation.

Direct imaging observations of possible dynamical upheavals in exoplanetary systems

Kalas, Paul

Giant planets are thought to form and persist on coplanar, circular orbits in the region of the protoplanetary disk cold enough to hold icy materials.  However, direct imaging observations reveal highly asymmetric debris disks and associated exoplanets that are inclined relative to these disks, have highly eccentric orbits, or are located at hundreds of au radius.  Here we present new HST/STIS images of several 10-100 Myr old systems that are consistent with dynamical upheavals.  We discovered one highly asymmetric dust disk around an M0 target in the 11 Myr-old Upper Sco association that could be a signature of a disk-planet perturbation.  Another target is Fomalhaut C (LP 876-10) where the new data test for a highly eccentric disk resulting from dynamical interactions with Fomalhaut A and B.  In addition, we show deep coronagraphic images of the HD 106906 planetary system that achieve higher signal-to-noise and a smaller inner working angle than previous HST/ACS optical observations.  The very extreme vertical and radial disk asymmetries of this 13 Myr-old Lower Centaurus-Crux debris disk indicate a recent dynamical upheaval involving a stellar flyby. 

From Filaments to Molecular Clouds and Protostellar Systems - what is the Role of the Magnetic Field?

Koch, Patrick

The role of the magnetic (B-) field in the star-formation process is highly debated. How important is the magnetic field in the presence of gravity and turbulence? Conclusive observational results have been scarce due to both limited available data anddue to the generally challenging measurements requiring very sensitive observations.We present observational results illustrating the role of the B-field on three representative scales in the star-formation process: (1) the filamentary-scale infrared dark cloud G34.Here, the local B-field correlates with the local velocity gradients on the largest scales.Based on a benchmark analysis that quantifies the various energy components we arguethat a different relative importance between B-field, turbulence, and gravity leads to  different observed fragmentation types on a next smaller scale; (2) the molecular-cloud-scale in the high-mass star-forming region W51. Here, increasingly higher resolutions fromthe SMA to ALMA resolve new B-field sub-structures. In particular, we see zones of symmetrically converging B-field lines, cometary-shaped satellite cores, local collapse features, and a possible new phenomenon of magnetic channelling; (3) the protostellar-source-scale in B335. Here, we provide evidence for magnetic braking from detailed high-resolution observations of the kinematics of neutral and ionized gas tracers. Besides these textbook cases on three different scales, we further present statistical resultsfrom a 50-source sample of molecular clouds that reveal generic B-field features and a systematically locally varying importance of the B-field versus gravity.

ALMA view of a cold cloud: unbound cores with chemical differentiation

Zahorecz, Sarolta

Herschel and Planck detected cold, dense clouds in emission throughout the Galaxy. Unlike targeted and area-limited surveys toward the inner part of the Galaxy, these new observations provided an unbiased catalog of the star forming clumps in the outer part of the Galaxy also. We have examined the physical properties of a homogeneous Galactic cold core sample obtained with the Planck satellite across the Galactic plane with the use of Herschel Hi-GAL observations. We calculated and analyzed the basic physical parameters of 48 Planck clumps as a function of location within the Galaxy. About 25% of the clumps are massive enough to form high-mass stars and star clusters. Planck clumps toward the Galactic center region show higher peak column densities and higher average dust temperatures than those of the clumps in the outer Galaxy. Based on our data, the Hi-GAL data showed no apparent differences in the properties of Planck clumps with and without star formation.We performed a high-resolution follow-up study of G191.51-0.76. It has a network of filaments converging into a central clump forming a hub-filament system and it does not show 70 micron sources making it a younger, scaled-down version of massive hub-filament systems, e.g. IRDC SDC13, G33.92+0.11. We observed the continuum, N2H+, HNC and 13CS emission toward it with ALMA to determine its small-scale physical structure and level of fragmentation. We identified two dense low-mass clumps (with a radius of 0.08pc) based on the SCUBA-2 data. These clumps further fragment at higher-angular resolution into four main dense cores (with a radius of 0.02pc) and a few small fragments detected only in selected tracers. No continuum source is detected in our high-sensitivity images of ALMA. The dense cores show chemical differentiation: while the N1 core is the youngest with bright HNC emission, the southern region is the most evolved with some evidence of CO depletion present in its hosting clump.

On the asymmetric features in circumstellar disks

Tang, Ya-Wen

Current detection of exoplanets is mostly obtained at optical and near IR wavelengths toward disks where dense gas has been dissipated. In order to look for planets at earlier evolutionary stage, indirect evidences are invoked, such as rings of dust free region within dense disks, or spiral patterns. With the starting of ALMA early science observations, these indirect evidences at the millimeter (mm) and sub-mmm wavelengths have been detected in several disks. In this poster, we report high angular resolution (0.1") observations with ALMA of the 1.3 mm continuum and 12CO J=2-1 emission from the inner 100 AU of the disk surrounding the Herbig Ae star AB Aurigae. The continuum emission shows three distinct feature: a compact (~ 2 au) dust disk around the star, the asymmetric dust ring at 120 AU, and previously undetected extended emission about 30 AU around the star along the rotation axis of the system. The CO emission is dominated by two prominent spiral-like arms. After correction for the large scale flux resolved out by these observations, these arms appear to be about twice brighter than their surrounding medium. Their kinematics is consistent with Keplerian rotation at an inclination of 30 degree. The apparent two arm spiral pattern is best explained by tidal disturbances created by an unseen companion located at 60--80 au, with dust confined in the pressure bumps created outside this companion orbit. However, the residual continuum emission, coinciding with the peak CO brightness and a large pitch angle of the spiral at this location, suggests another hidden object here, which would help to explain the overall emptiness of the cavity. Alternative mechanisms to excite the spirals are discussed. The origin of the large pitch angle detected here remains puzzling.

Deuteration of formaldehyde - an important precursor of hydrogenated complex organic molecules - during star formation in our Galaxy

Zahorecz, Sarolta

The formation of deuterated molecules is favoured at low temperatures and high densities. Therefore, the deuteration fraction is expected to be enhanced in cold, dense prestellar cores and to decrease after protostellar birth. Previous studies have shown that the deuterated forms of species such as N2H+ (formed in the gas phase) and CH3OH (formed on grain surfaces) can be used as evolutionary indicators and to constrain their dominant formation processes and timescales. Formaldehyde (H2CO) is crucial in any chemical networks because it is very abundant and it is an important precursor of hydrogenated complex organic molecules (COMs). Non-energetic (atom bombardment) reactions offer one of the pathways toward COM formation at temperatures as low as 10 K.H2CO and its deuterated forms can be produced both in the gas phase and on grain surfaces. However, the relative importance of these two chemical pathways is unclear. Comparison of the deuteration fraction of H2CO with respect to that of N2H+, NH3, and CH3OH can help us to understand its formation processes and timescales. With the new SEPIA Band 5 receiver on APEX, we have observed rotational lines of HDCO and D2CO at 193 GHz and 175 GHz toward eleven massive star-forming regions hosting objects at different evolutionary stages: high-mass starless cores, high-mass protostellar objects, and ultracompact HII regions.Our observations show that singly and doubly deuterated H2CO is detected toward all sources and that the deuteration fraction of H2CO increases from the starless to the protostellar phase and then sharply decreases in the latest evolutionary stage. H2CO may display a similar fractionation pattern as that of CH3OH in massive young stellar objects. This finding suggests that solid-state reactions dominate its formation.

Searching for Methylamine in Orion-KL using ALMA archival data

Minamoto, Harumi

Methylamine (CH3NH2) is the simplest amine and thought to be potential interstellar precursors to the amino acid glycine (NH2CH2COOH). It is confirmed by the experiment that the reaction of methylamine with CO2 in water ice yields glycine under UV irradiation. In terms of exploration in the Solar system, this molecule has been detected in comet 81P/Wild 2 in the Stardust mission and comet 67P/Churyumov-Gerasimenko in the Rosetta mission. However, a robust detection of methylamine has been reported only in Sgr B2(N) while a variety of complex organic molecules have been detected by radio observation in molecular clouds so far. To search for methylamine, we focused on the Orion Kleinmann–Low nebula (Orion-KL), which is known as the nearest high-mass star-forming region and one of the most prolific sources of line emission of a variety of complex organic molecules. Because of its richness in chemical composition, it also has been regarded as a suitable target for molecular line survey in the interstellar medium. We used the ALMA Science Verification(SV) data and Cycle 2 archival data toward Orion-KL at Band 6, and several candidate spectral features of methylamine were found. These exhibit a compact emission at the center of the Hot core, with the signal-to-noise ratio of 10 and Vpeak ~ 5 km/s, although the possibility of contamination by other molecular line emissions is not excluded. Also the frequency coverage of the Cycle 2 data is not wide enough so that the transition lines of this species, which are expected to be relatively strong, cannot be identified in the data. Therefore, we need to merge the SV data to cover a wider frequency. In order to obtain the precise intensity of the lines, we performed statistical analysis to subtract the continuum emission.For the robust detection, we will discuss the physical state of the candidate lines, such as the distribution of temperature and column density, and a rotational diagram analysis.


Monfredini, Thiago

As the characterization of extrasolar planetary atmospheres is a new frontier in exoplanetary science, there has been a growing interest on determining what properties of atmospheric chemistry are indicative of the presence of a biosphere. Some molecules, like molecular oxygen and ozone have been proposed as possible evidence of the presence of life; however, their detectability fluctuates, and they are capable of being produced abiotically, leading to the possibility of false positives. Species known as volatile organic compounds (VOCs), such as isoprene and other terpenoids, are emitted in significant amount by trees and other vegetations. The emission of biogenic VOCs can play an important role in the photophysics and photochemistry of a atmosphere, affecting its oxidative capacity. To understand the molecular stability of VOCs in the atmosphere, we have measured the absolute photoionizing cross-section of these molecules, using an ionizing chamber and ion-trap spectrometer, with UV, EUV and soft X-ray radiation (3-300 eV) from the Toroidal Grating Monochromator (TGM) beamline of the Brazilian Synchrotron Light Laboratory (LNLS), to simulate the radiation field of astrophysical situations. The ionizing chamber has four ion-collectors, two guard-electrodes, a repeller and a pair of secondary electron deflectors in a cylindrical symmetry. It was determined the optimized voltage of the ion collector as 20 V from the plateau of ion current versus applied potential curve, through the ionization of argon, nitrogen and xenon with pressures between 10-8 and 10-6 torr. In our preliminary results, we have determined photoionizing cross-section of toluene at energies of 102 eV and 280 eV produces. Also, these results sugest that the photofragmentation of toluene at these energies produces high rates of double ionizied fragments.

Konkoly optical catalog of young stars

Varga-Verebelyi, Erika

We present a new and so far most complete catalog of optically selected young stars and give a statistical overview of the Galactic star forming regions within our 2-kpc environment.The basis of this work is an extensive literature search for young stars in all the known star forming regions included in both volumes of the Handbook of Star Forming Regions.We collected data on  known young (< 10 Myr) stars detected in optical bands.The catalog contains information (such as sky coordinates, name of the stars, name of the enclosing star forming regions, the identification methods, references and binarity) about 12 600 YSOs and it is already in use by the Gaia Photometric Science Alerts Team to help identify variable YSOs. The catalog was cross-correlated with Gaia DR2  and obtained flux and distance estimations for 86% of the stars.

Near-Earth object population and formation of lunar craters during the last billion of years

Ipatov, Sergei

We analyzed diameters of lunar craters in the region of the Oceanus Procellarum with age TOS<1.1 Gyr. The ratio rOS of the area of the considered region to the full surface of the Moon is 0.176. Based on the formula (16) from [1] we concluded that the diameter D of the crater that is produced by an impactor with a diameter di=1 km is 19.1 km and 18.4 km for the impact velocity equal to 19.3 km/s and 18 km/s, respectively. The number Nobs of craters with D greater than 18 or 19 km in the considered region is 49. The number N1 of near-Earth objects (NEOs) with diameter d>1 km is considered to be about 920. The characteristic time TE elapsed before a collision of a NEO with the Earth is estimated to be about 100 Myr (up to 120 Myr). The ratio pEM of probabilities of collisions of NEOs with the Earth to that with the Moon is about 20. Based on the above values we estimated the number of impacts of NEOs with d>1 km onto the considered lunar region as Nest=N1·rOS·TOS/(TE·pEM)˜920·0.176·1.1/(0.1·20)˜89. The ratio Nest/Nobs is 1.8. For greater values of TE and pEM, the ratio can be a little smaller, but probably it is still greater than 1.5. The above estimates show that the number Nobs of observed craters is less than the estimated number Nest, i.e. the mean value of TE·pEM calculated for the last billion of years could be greater than its present value, or N1 or TOS should be smaller for calculation of Nest. A recent catastrophic disruption of a large main-belt asteroid [2] could increase N1 compared to its mean value for a whole 1 Gyr interval. The difference in the values of Nest and Nobs can be also caused by that craters with a greater age less survive. Results of our analysis of the number of craters of different sizes are in accordance with the earlier conclusion that the number of impactors with a diameter d>Dp is proportional to Dp-2/3. [1] Werner S.C., Ivanov B.A. Treatise on Geophysics (Second Edition),2015,10,327–365. [2] Bottke W. et al. Nature, 2007,449,48-53

Tracing the gas, dust and ice evolution in planetary systems with SPICA

Audard, Marc

SPICA, an infrared space mission operating in the mid and far-infrared has recently been selected for further study in the frame of ESA’s M5 call. SPICA will carry SAFARI, an infrared spectrometer operating from 34 to 230 µm (R˜300-11000), POL, an imaging polarimeter at 100, 200, and 350 µm, and SMI that will provide imaging spectroscopy with R˜100 and full-band slit-fed spectroscopy at R˜100-2,000 from 17 to 36µm, and R˜28,000 from 12 to 18µm. The SPICA telescope will be cooled down to about 8K, effectively suppressing most of the satellite's infrared thermal background, which will allow us to reach down to very low fluxes. SPICA will provide spectroscopic capabilities at a high sensitivity of 2-15 x1e-20 W/m2 (5s/1hr), about two orders of magnitude deeper than Herschel. One of the core science topics addressed by SPICA is "Tracing the gas, dust and ice evolution in planetary systems”. We present this topic to demonstrate the capabilities of SPICA.

A double cold core in Auriga-California Molecular Cloud

Zahorecz, Sarolta

A detailed study of the densest cold core in the Auriga-California Molecular Cloud is presented based on ammonia line measurements with the Effelsberg-100m telescope applying a radiative transfer model with two 3-dimensional spheres. Our high spectral resolution high S/N observations shows two different velocity components with a separation of 0.5km/s.Radiative transfer modeling of NH3 line emission were performed. We have used cppsimu, a non-LTE Monte-Carlo radiative transfer simulation. In this, each cell in the model box is essentially described by its gas content's density, kinetic temperature, line of sight and turbulent velocity components and the given species' abundance. Our model box, was constructed as the sum of two spherically symmetric density and temperature distributions in each cell, aiming to reproduce the observed double line profile. We used a Plummer-like profile to describe the spheres' density distributions. (A Bonnor-Ebert profile based fit yields mass estimates consistent with a Plummer one within 1 sigma, hence it qualitatively does not change our results.)The radiative transfer equation was then solved by cppsimu propagating photon packages through this box. It then produced mock spectra with a matched beam size and spacing to our Effelsberg-100m observations.These model spectra were optimized against our NH3 (1,1) and (2,2) data in 34 positions simultaneously by changing nine parameters in the model: kinetic temperatures, sizes, central densities, line of sight velocities and turbulent velocity components of each clumps independently and their separation perpendicular to the line of sight. The initial values of these and the line of sight velocities were based on measured ones derived from our observations.The model optimization was performed with a Bayesian-approach.

ARIEL - An ESA Space Mission to Focus on the Nature Of Exoplanets

Lueftinger, Theresa

ARIEL (Atmospheric Remote-sensing Exoplanet Large-survey) has recently been selected as the next medium-class science mission by the European Space Agency (ESA) due for launch in 2028. The goal of the ARIEL mission is to investigate the atmospheres of planets orbiting distant stars in order to address the fundamental questions on how planetary systems form and evolve and to investigate the composition of exoplanetary atmospheres.During its 4-year mission, ARIEL will observe 1000 exoplanets ranging from Jupiter- and Neptune-size down to super-Earth size, in a wide variety of environments, in the visible and the infrared. The main focus of the mission will be on warm and hot planets in orbits close to their star. Some of the planets may be in the habitable zones of their stars, however. The analysis of ARIEL spectra and photometric data will allow to extract the chemical fingerprints of gases and condensates in the planets’ atmospheres, including the elemental composition for the most favorable targets. The ARIEL mission has been developed by a consortium of more than 60 institutes from 15 ESA member state countries, including UK, France, Italy, Poland, Spain, the Netherlands, Belgium, Austria, Denmark, Ireland, Hungary, Sweden, Czech Republic, Germany, Portugal, with an additional contribution from NASA in the USA currently under study.

Star Formation Science Highlights from the Airborne Infrared Observatory SOFIA

Zinnecker, Hans

SOFIA, short for Stratospheric Observatory for InfraredAstronomy, has been observing the mid- and far-infrared skyin both the northern and the southern hemisphere since 2011,with dedicated broad-band cameras (FORCAST, HAWC+) andhigh-resolution spectrometers (GREAT, FIFI-LS, EXES). In this poster, we summarize some of the highlights of theseobservations:1) imaging:   -- IRc4, a new luminous protostar in the Orion BN/KL region   -- eps Eri, a solar system analog with a spatially resolved debris disk   -- the Rho Oph dust cloud and the geometry of its magnetic field2) spectroscopy:   -- infall motion (collapse) of an ATLAS-GAL protocluster cloud   -- a far-infrared luminosity outburst (factor 10) and light echo      due to episodic disk accretion in the massive YSO S255-IRS3   -- water in absorption (6.1 mu ground state ro-vib transition)      in the AFGL 2591 protostellar envelopeSOFIA also discovered a number of new light molecules in the ISMand in protostellar envelopes, such as SH, OH, OD, H2D+, HD2+, all in absorption against strong far-IR continuum sources(eg. IRAS 16293 or W49N).SOFIA is currently the only far-IR Observatory for years to comeand is open world-wide to Cycle 7 proposals (deadline 7 Sept 2018).  


Monfredini, Thiago

The investigation of microbial life and/or inorganic biosignatures on Mars has been done mainly by the study of analogue environments on Earth. The nature of the ferriferous regions in Brazil seems to be suitable, as a substantial sources of extremophiles (Duarte et al, 2012) and potential source of inorganic biosignatures. This work is aimed to improve the knowledge needed to test the possibility of present or evidence of past life on Mars by characterizing samples of the iron-rich soil of the region of Diamantina, located at the center of Brazil. This characterization consists of examining the atomic and molecular compositions and the structural, mechanical and optical properties of the soil. This is done by applying different experimental techniques, such as thermo-gravimetry, electron microscopy and X-ray spectroscopy. The molecular and atomic structure had been measured through, both, X-ray diffraction and fluorescence at LNLS (Brazilian Synchrotron Light Laboratory - Campinas). Also, the volatile content was investigated through thermo-gravimetry in a high-temperature furnace and by H:C:N analysis. The X-ray diffractogram is dominated by cristalline silicon oxide with low contribution of an amorphous phase. Also, there is no strong evidence of phylosilicates (clay minerals). Thermo-gravimetry showed weight losses of just ~1 wt% at 600oC. For comparison, JSC Mars-1, a well-known Martian analog soil, has a large volatile content, presenting losses of 21.1 wt% in the same conditions. It also confirms the abscence of phylosilicates. Viking in situ experiments of the Martian soil released ~1.0 wt% water from samples heated at 500oC, which suggest that Martian regolith is also extremely dry (Biemann et al, 1977). So, our preliminary results showed good evidence that Diamantina's soil can be a good candidate for Martian simulant, just as JCS Mars-1 and JMSS-1.

The TOP-SCOPE survey of Planck Galactic Cold Clumps: The 200 brightest compact sources of Planck

Bogner, Rebeka

The Planck all-sky submillimetre observations have made it possible to study Galactic cold clumps in diverse environments, to probe dust properties and to examine the earliest stages of star formation. The TOP-SCOPE joint survey program aims to statistically study the evolution of molecular clouds and the initial conditions of star formation in a wide variety of environments targeting around 2000 Planck Galactic Cold Cores (PGCCs) in CO isotopologues and around 1000 PGCCs in 850 micrometer continuum emission. In this work we carried out an investigation of the 200 brightest compact sources detected by Planck. These are not necessarily PGCCs, most of them are star forming; out of them 80 have been observed in SCOPE. Using Herschel and JCMT observations we investigated the dust properties of the cores, making column density and dust temperature maps. We also investigated the young stellar objects in the vicinity of the sources to examine their influence on such star-forming sites. We aim to compare the properties of this sample to PGCCs to see how star formation efficiency, clustering behavior and core masses evolve with time.

Population Synthesis of Planets Around M Dwarfs

Schlecker, Martin

Planet Population Synthesis is a statistical approach to study the conditions necessary for planet formation and evolution. The utilization of the Bern model of planet formation and evolution (Alibert et al. 2013) within a population synthesis framework (Mordasini et al. 2009) has led to testable predictions, such as the now-confirmed minimum in the planetary mass distribution between a few Earth masses and ~40 Earth masses (Mordasini et al. 2009).Ongoing efforts aim at applying this technique to the observational sample of the CARMENES survey, which searches for Earth-mass planets around nearby M-dwarf stars. By confronting our simulations with the planets and non-detections in the sample, we can improve our understanding of key processes in planet formation around low-mass stars. For this purpose, we extend our model to the regime of late-type stars, accounting for the different conditions in their protoplanetary disks. Changes to the original setup include a smaller inner disk radius, a down-scaled disk mass distribution, distinct morphologies for the solid disk and the gas disk, and N-body interaction between protoplanets.As a test case, we create a population of systems with a host star mass of 0.1 solar masses and compare it to observables of the TRAPPIST-1 multi-planet system (Gillon et al. 2017). By randomly drawing initial locations for 50 lunar-mass planetary embryos from a log-uniform distribution between 0.02 au and 10 au, we find that many features of this unique system can be reproduced. Using the resulting mean planetary mass as a metric, we find a domain in initial disk solid mass and disk extent favorable for the formation of systems similar to TRAPPIST-1.

The MESAS Project – Stellar Atmospheres as a Source of Flux Bias in Debris Disks

White, Jacob

The planet formation process shapes the morphology and grain size distribution of circumstellar disks, encoding the formation history of a given system. Remnants of planet formation, such as comets and asteroids, collisionally evolve and can replenish the dust and small solids that would otherwise be cleared on short timescales. These grains are observed through their thermal emisison at submm to cm wavelengths.The spectrum of the mm/cm emission reveals details of the grain population. However, one confounding parameter in studying these grains around stars is the stars themselves. The emission from stars in the mm/cm is nontrivial and generally not well-constrained. I will present examples of debris systems (HD 141569 and Fomalhaut) studied by ALMA and the VLA, in which unconstrained stellar emission may be contributing to the observed flux densities. Such contamination in turn biases the inferred emission from the disk and the corresponding dust properties. In some cases, the behavior of the observed A/B stars can exhibit an emission profile that has similarities to that of the Sun's mm/cm emission, although the same processes are not thought to necessarily occur in the atmospheres of massive stars.To address the uncertainty in stellar emission at mm/cm wavelengths, we present ongoing radio observations (JCMT, SMA, VLA) of Sirius A, which is a bright, nearby star with no known debris. We seek to use this system to set an observationally determined standard for stellar atmosphere modeling and debris disk studies around A stars, as well as to take the first step toward characterizing potential intrinsic uncertainty in stellar emission at these wavelengths. This presentation highlights the effort to characterize stellar atmospheres through a project known as MESAS (Measuring the Emission of Stellar Atmospheres at Submillimeter/millimeter wavelengths) which is imperative to the success of current and future debris disk studies.

Characterizing the atmospheres of giant exoplanets

Khalafinejad, Sarah

The application of the transmission spectroscopy method during a transit of an exoplanet has allowed us to study the chemical composition of exoplanetary atmospheres. Among evolved exoplanets, hot Jupiters have the largest and most extended atmospheres. Hence, considering current observing facilities, they are great targets for carrying out atmospheric characterization. These objects allow us to improve our observing techniques and re ne our models to characterize other types of exoplanetary atmospheres such as the atmospheres of Earth analogues. To reach this stage, one of the most important steps in the data analysis is to disentangle the host star features from those of the planet. This is particularly important for the characterization of small and rocky exoplanets, which so far have mainly been detected around active M dwarfs. In this research, we used single transit observations of HD 189733b (with UVES/VLT) and WASP-17b (with MIKE/Magellan) as test targets. We obtained their high-resolution transmission spectra at sodium lines. In this procedure, we rst considered the e ects of stellar aring activity and stellar di erential limb-darkening. Then, as a novel approach, we accounted for the changing planetary radial velocity on the atmospheric excess light curves. In the second stage of the work, after the detection of sodium in these giant exoplanets, the transmission spectra are compared with atmospheric models to constrain the temperature and radius of the exoplanet. We are currently improving our framework to additionally consider the e ects of stellar spots. Hence, it can be used for applications on lower-mass targets.

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