scholarly journals The Chemistry of Nearby Disks

2015 ◽  
Vol 10 (S314) ◽  
pp. 143-148
Author(s):  
Karin I. Öberg
Keyword(s):  
Planet Formation ◽  
Initial Conditions ◽  
Young Star ◽  
Young Stars ◽  
Chemical Structures ◽  
Lessons Learnt ◽  
Trace Species ◽  
Molecular Studies

AbstractThe gas and dust rich disks around young stars are the formation sites of planets. Observations of molecular trace species have great potential as probes of the disk structures and volatile compositions that together regulate planet formation. The disk around young star TW Hya has become a template for disk molecular studies due to a combination of proximity, a simple face-on geometry and richness in volatiles. It is unclear, however, how typical the chemistry of the TW disk is. In this proceeding, we review lessons learnt from exploring the TW Hya disk chemistry, focusing on the CO snowline, and on deuterium fractionation chemistry. We compare these results with new ALMA observations toward more distant, younger disks. We find that while all disks have some chemical structures in common, there are also substantial differences between the disks, which may be due to different initial conditions, structural or chemical evolutionary stages, or a combination of all three.

scholarly journals Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): A close low-mass companion to ET Cha

2020 ◽  
Vol 642 ◽  
pp. A119
Author(s):  
C. Ginski ◽  
F. Ménard ◽  
Ch. Rab ◽  
E. E. Mamajek ◽  
R. G. van Holstein ◽  
...  
Keyword(s):  
Planet Formation ◽  
Thermal Emission ◽  
Initial Conditions ◽  
Scattered Light ◽  
Primary Component ◽  
Young Stars ◽  
High Contrast ◽  
Evolution Study ◽  
Disk Evolution ◽  
Low Mass

Context. To understand the formation of planetary systems, it is important to understand the initial conditions of planet formation, that is, the young gas-rich planet forming disks. Spatially resolved, high-contrast observations are of particular interest since substructures in disks that are linked to planet formation can be detected. In addition, we have the opportunity to reveal close companions or even planets in formation that are embedded in the disk. Aims. In this study, we present the first results of the Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS), an ESO/SPHERE large program that is aimed at studying disk evolution in scattered light, mainly focusing on a sample of low-mass stars (< 1 M⊙) in nearby (∼200 pc) star-forming regions. In this particular study, we present observations of the ET Cha (RECX 15) system, a nearby “old” classical T Tauri star (5−8 Myr, ∼100 pc), which is still strongly accreting. Methods. We used SPHERE/IRDIS in the H-band polarimetric imaging mode to obtain high spatial resolution and high-contrast images of the ET Cha system to search for scattered light from the circumstellar disk as well as thermal emission from close companions. We additionally employed VLT/NACO total intensity archival data of the system taken in 2003. Results. Here, we report the discovery, using SPHERE/IRDIS, of a low-mass (sub)stellar companion to the η Cha cluster member ET Cha. We estimate the mass of this new companion based on photometry. Depending on the system age, it is either a 5 Myr, 50 MJup brown dwarf or an 8 Myr, 0.10 M⊙ M-type, pre-main-sequence star. We explore possible orbital solutions and discuss the recent dynamic history of the system. Conclusions. Independent of the precise companion mass, we find that the presence of the companion likely explains the small size of the disk around ET Cha. The small separation of the binary pair indicates that the disk around the primary component is likely clearing from the outside in, which explains the high accretion rate of the system.

scholarly journals Chasing disk dispersal indicators: the origin of the [OI] low-velocity components from young stars

2013 ◽  
Vol 8 (S299) ◽  
pp. 226-227
Author(s):  
Elisabetta Rigliaco ◽  
Ilaria Pascucci ◽  
Uma Gorti ◽  
Suzan Edwards ◽  
David Holenbach
Keyword(s):  
Velocity Component ◽  
Planet Formation ◽  
Young Star ◽  
Young Stars ◽  
Low Velocity

AbstractUnderstanding how a disk surrounding a young star evolves and disperses is crucial in order to understand the subsequent planet formation. In this proceeding, we summarize the results reported by Rigliaco et al. (2013) on the origin of the [OI] low-velocity component as a possible disk dispersal indicator.

scholarly journals Double trouble: Gaia reveals (proto)planetary systems that may experience more than one dense star-forming environment

2020 ◽  
Vol 501 (1) ◽  
pp. L12-L17
Author(s):  
Christina Schoettler ◽  
Richard J Parker
Keyword(s):  
Planetary Systems ◽  
Young Star ◽  
Young Stars ◽  
Orion Nebula ◽  
External Effects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ejection Process ◽  
Runaway Stars

ABSTRACT Planetary systems appear to form contemporaneously around young stars within young star-forming regions. Within these environments, the chances of survival, as well as the long-term evolution of these systems, are influenced by factors such as dynamical interactions with other stars and photoevaporation from massive stars. These interactions can also cause young stars to be ejected from their birth regions and become runaways. We present examples of such runaway stars in the vicinity of the Orion Nebula Cluster (ONC) found in Gaia DR2 data that have retained their discs during the ejection process. Once set on their path, these runaways usually do not encounter any other dense regions that could endanger the survival of their discs or young planetary systems. However, we show that it is possible for star–disc systems, presumably ejected from one dense star-forming region, to encounter a second dense region, in our case the ONC. While the interactions of the ejected star–disc systems in the second region are unlikely to be the same as in their birth region, a second encounter will increase the risk to the disc or planetary system from malign external effects.

Exploring the dust ring in the circum-binary disc around GG Tau A

2021 ◽  
Author(s):  
Claudia Toci ◽  
Simone Ceppi ◽  
Nicolas Cuello ◽  
Giuseppe Lodato ◽  
Cristiano Longarini ◽  
...  
Keyword(s):  
Binary Systems ◽  
Planet Formation ◽  
Initial Conditions ◽  
Scattered Light ◽  
Complex Structure ◽  
Semimajor Axis ◽  
Continuum Emission ◽  
Orbital Parameter ◽  
Semi Major Axis ◽  
Multiple Systems

&lt;p&gt;Binaries and multiple systems are common among young stars (Reipurth et al. 2014). These stars are often surrounded by discs of gas and dust, formed due to the conservation of angular momentum of the collapsing cloud, thought to be the site of planet formation.&lt;br /&gt;In the case of binary systems, three discs can form: an outer disc surrounding all the stars (called circumbinary disc), and two inner discs around the stars. As circumbinary planets have recently been discovered by Kepler (see e.g., Martin 2018, Bonavita &amp; Desidera 2020), it is crucial to understand the dynamics and evolution of circumbinary discs to better understand the initial conditions of planet formation in multiple systems.&lt;br /&gt;The GG Tau A system is an example of a young multiple T Tauri star. The binary is surrounded by a bright disc, observed in the continuum emission at different wavelengths (see e.g., Guilloteau et al. 1999; Dutrey et al. 2014; Phuong et al. 2020b) and in scattered light (e.g., Duchene et al. 2014, Keppler et al. 2020). The disc extends in the dust from 180 to 280 au from the center of mass, and in the gas up to 850 au. The inner (&lt;180 au) part is depleted in gas and dust. Scattered light images show a complex structure in the inner part of the disc, with arcs and filamentary structures connecting the outer ring with the arcs and three shadows.&lt;br /&gt;Two different configurations are possible fitting the proper motion data for the system: a co-planar case with a low eccentricity binary with a semi-major axis of 34 au, explored by Cazzoletti et al. 2017 and Keppler et al. 2020, and a misaligned case (i=30) with an eccentric binary (e=0.45) and a wider semimajor axis of 60 au (Aly et al.2018). At the state of the art, all these analyses focused on the gas dynamics only.&lt;br /&gt;We will show the results of new 3D SPH simulations of dust and gas performed with the code PHANTOM, devised to test the two possible scenarios. We will describe the dynamics of the system in the two cases, comparing our models with observational results in order to better constraint the orbital parameter of the GG Tau A system. Our predictions will guide future observing campaigns and shed light on the complex evolution of discs in triple stellar systems.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Probing AU-scale Structure using Spectro-astrometry

2004 ◽  
Vol 221 ◽  
pp. 417-424 ◽  
Author(s):  
Michihiro Takami ◽  
Jeremy Bailey ◽  
Antonio Chrysostomou ◽  
Motohide Tamura ◽  
Hiroshi Terada
Keyword(s):  
Adaptive Optics ◽  
Main Sequence ◽  
Planet Formation ◽  
Hubble Space Telescope ◽  
Circumstellar Disks ◽  
Scale Structure ◽  
Young Stars ◽  
Space Telescope ◽  
Powerful Technique ◽  
Circumstellar Environment

The circumstellar environment within 10 AU of young stars are of particular interest for star and planet formation. Unfortunately, present imaging facilities such as the Hubble Space Telescope or adaptive optics on 10-m telescopes cannot resolve this region. We have proved that “spectro-astrometry” is a powerful technique for discovering pre-main-sequence binaries, determining kinematics of outflows and providing evidence for gaps in circumstellar disks — all down to AU scales. In this paper, we summarise our progress to date.

scholarly journals Star Clusters and Stellar Populations of the M31 Disk as Viewed by HST

2002 ◽  
Vol 207 ◽  
pp. 149-151
Author(s):  
Benjamin F. Williams ◽  
Paul W. Hodge
Keyword(s):  
Star Clusters ◽  
Stellar Populations ◽  
Young Star ◽  
Young Stars ◽  
New Method ◽  
Data Archive ◽  
Stellar Photometry ◽  
Identification Method ◽  
Ob Associations ◽  
Young Star Clusters

We present a new method for finding associations of young stars in M31 using broadband WFPC2 data from the HST data archive. Applying our identification method to 13 WFPC2 fields, covering an area of ∼60 arcmin2, has revealed 80 new candidate young star clusters in these portions of the M31 disk. Most of these clusters are small (≳5 pc) young (∼10–200 Myr) star groups located within large OB associations. We have estimated the reddening values and the ages of each candidate individually by fitting isochrones to the stellar photometry. We provide a catalogue of the candidates including rough approximations of their reddenings and ages.

scholarly journals An UXor among FUors: extinction-related brightness variations of the young eruptive star V582 Aur

2018 ◽  
Vol 14 (S345) ◽  
pp. 390-392
Author(s):  
P. Ábrahám ◽  
Á. Kóspál ◽  
M. Kun ◽  
O. Fehér ◽  
G. Zsidi ◽  
...  
Keyword(s):  
Near Infrared ◽  
Planet Formation ◽  
Accretion Rate ◽  
Initial Conditions ◽  
Early Evolution ◽  
Line Of Sight ◽  
Infrared Measurements ◽  
Bona Fide

AbstractThe early evolution of Sun-like stars may be interspersed by energetic FU Orionis (FUor) type accretion outbursts. We analysed eight years of photometric and spectroscopic variability of V582 Aur, a bona fide FUor, in outburst. While the accretion rate derived from near-infrared measurements was constant, radical brightness changes occurred due to dust clumps crossing the line of sight. The brightness minima resemble the variability patterns of the UXor phenomenon. Orbiting density enhancements or short-lived clumps moving in and out of the line-of-sight may explain these observations. Our message is that during FUor outbursts the inner disk is a dynamically active place, affecting the initial conditions for planet formation.

scholarly journals Chemistry in the Envelopes around Massive Young Stars

2002 ◽  
Vol 12 ◽  
pp. 146-148
Author(s):  
Ewine F. van Dishoeck ◽  
Floris F.S. van der Tak
Keyword(s):  
Young Star ◽  
Young Stars ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Chemical Studies ◽  
H Ii Region ◽  
Infrared Wavelengths ◽  
Collapse Phase

AbstractRecent chemical studies of high-mass star-forming regions at submillimeter and infrared wavelengths reveal large variations in the abundances depending on evolutionary state. Such variations can be explained by freezing out of molecules onto grains in the cold collapse phase, followed by evaporation and high-temperature chemical reactions when the young star heats the envelope. Thus, the chemical composition can be a powerful diagnostic tool. A detailed study of a set of infrared-bright massive young stars reveals systematic increases in the gas/solid ratios and abundances of evaporated molecules with temperature. This ‘global heating’ plausibly results from the gradual dispersion of the envelopes. We argue that these objects form the earliest phase of massive star formation, before the ‘hot core’ and ultracompact H II region phase.

Implications of stellar activity for exoplanetary atmospheres

2010 ◽  
Vol 9 (4) ◽  
pp. 239-243 ◽  
Author(s):  
P. Odert ◽  
M. Leitzinger ◽  
A. Hanslmeier ◽  
H. Lammer ◽  
M.L. Khodachenko ◽  
...  
Keyword(s):  
Extreme Ultraviolet ◽  
Planetary Atmospheres ◽  
Young Star ◽  
Young Stars ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
X Ray ◽  
History Of ◽  
Low Mass ◽  
Exoplanetary Atmospheres

AbstractStellar X-ray and extreme ultraviolet (XUV) radiation is an important driver of the escape of planetary atmospheres. Young stars emit high XUV fluxes that decrease as they age. Since the XUV emission of a young star can be orders of magnitude higher compared to an older one, this evolution has to be taken into account when studying the mass-loss history of a planet. The temporal decrease of activity is closely related to the operating magnetic dynamo, which depends on rotation and convection in Sun-like stars. Using a sample of nearby M dwarfs, we study the relations between age, rotation and activity and discuss the influence on planets orbiting these low-mass stars.

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