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

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.

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ISPY-NACO Imaging Survey for Planets around Young stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937000 ◽

2020 ◽

Vol 635 ◽

pp. A162 ◽

Cited By ~ 1

Author(s):

R. Launhardt ◽

Th. Henning ◽

A. Quirrenbach ◽

D. Ségransan ◽

H. Avenhaus ◽

...

Keyword(s):

Planet Formation ◽

Scattered Light ◽

Young Stars ◽

Giant Planets ◽

Occurrence Rate ◽

High Contrast ◽

Contrast Imaging ◽

Direct Imaging ◽

Target List ◽

Low Mass

Context. The occurrence rate of long-period (a ≳ 50 au) giant planets around young stars is highly uncertain since it is not only governed by the protoplanetary disc structure and planet formation process, but also reflects both dynamical re-structuring processes after planet formation as well as possible capture of planets not formed in situ. Direct imaging is currently the only feasible method to detect such wide-orbit planets and constrain their occurrence rate. Aims. We aim to detect and characterise wide-orbit giant planets during and shortly after their formation phase within protoplanetary and debris discs around nearby young stars. Methods. We carry out a large L′-band high-contrast direct imaging survey for giant planets around 200 young stars with protoplanetary or debris discs using the NACO instrument at the ESO Very Large Telescope on Cerro Paranal in Chile. We use very deep angular differential imaging observations with typically >60° field rotation, and employ a vector vortex coronagraph where feasible to achieve the best possible point source sensitivity down to an inner working angle of about 100 mas. This paper introduces the NACO Imaging Survey for Planets around Young stars (NACO-ISPY), its goals and strategy, the target list, and data reduction scheme, and presents preliminary results from the first 2.5 survey years. Results. We achieve a mean 5 σ contrast of ΔL′ = 6.4 ± 0.1 mag at 150 mas and a background limit of L′bg = 16.5±0.2 mag at >1.′′5. Our detection probability is >50% for companions with ≳8 MJup at semi-major axes of 80–200 au and >13 MJup at 30–250 au. It thus compares well to the detection space of other state-of-the-art high-contrast imaging surveys. We have already contributed to the characterisation of two new planets originally discovered by VLT/SPHERE, but we have not yet independently discovered new planets around any of our target stars. We have discovered two new close-in low-mass stellar companions around R CrA and HD 193571 and report in this paper the discovery of close co-moving low-mass stellar companions around HD 72660 and HD 92536. Furthermore, we report L′-band scattered light images of the discs around eleven stars, six of which have never been imaged at L′-band before. Conclusions. The first 2.5 yr of the NACO-ISPY survey have already demonstrated that VLT/NACO combined with our survey strategy can achieve the anticipated sensitivity to detect giant planets and reveal new close stellar companions around our target stars.

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Timescales of Disk Evolution and Planet Formation

Symposium - International Astronomical Union ◽

10.1017/s007418090021783x ◽

2004 ◽

Vol 202 ◽

pp. 196-198

Author(s):

Ray Jayawardhana

Keyword(s):

Planet Formation ◽

Circumstellar Disks ◽

Young Stars ◽

Disk Evolution ◽

Low Mass ◽

Tw Hydrae Association ◽

Dust Disks

It has been suggested that circumstellar disks evolve from dense, actively accreting structures to low-mass, replenished remnants. During this transition, grains may assemble into planetesimals, or the disk may be cleared by newborn planets. Recently identified nearby groups of young stars provide valuable laboratories for probing disk evolution. I discuss the properties of dust disks in the TW Hydrae Association and the MBM 12 cloud, and compare the results to other studies of disk evolution and planet formation timescales.

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

10.5194/epsc2021-831 ◽

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

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. 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 & 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. 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 (<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. 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. 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. &#160;

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Terrestrial planet formation in low-mass disks: dependence with initial conditions

Proceedings of the International Astronomical Union ◽

10.1017/s174392131400831x ◽

2014 ◽

Vol 9 (S310) ◽

pp. 218-219

Author(s):

M. P. Ronco ◽

G. C. de Elía ◽

O. M. Guilera

Keyword(s):

Gas Phase ◽

Analytical Model ◽

Ad Hoc ◽

Planet Formation ◽

Initial Conditions ◽

Planetary Systems ◽

Terrestrial Planet ◽

Initial Distribution ◽

Protoplanetary Disk ◽

Low Mass

AbstractIn general, most of the studies of terrestrial-type planet formation typically use ad hoc initial conditions. In this work we improved the initial conditions described in Ronco & de Elía (2014) starting with a semi-analytical model wich simulates the evolution of the protoplanetary disk during the gas phase. The results of the semi-analytical model are then used as initial conditions for the N-body simulations. We show that the planetary systems considered are not sensitive to the particular initial distribution of embryos and planetesimals and thus, the results are globally similar to those found in the previous work.

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Evolution of Young Stars and Their Disks in Serpens

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310011221 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 731-731

Author(s):

Isa Oliveira ◽

Bruno Merín ◽

Klaus Pontoppidan ◽

Ewine van Dishoeck

Keyword(s):

Initial Conditions ◽

Formation Rate ◽

Protoplanetary Disks ◽

Small Region ◽

Young Stars ◽

Young Stellar Objects ◽

Evolutionary Sequence ◽

Infrared Excess ◽

Mid Infrared ◽

Disk Evolution

AbstractUnbiased, flux-limited surveys of protoplanetary disks and their parent stars currently exist for only a few clouds, primarily Taurus and IC 348, selected primarily by optical and near-IR data. Such surveys are essential to address questions of disk evolution as a function of stellar parameters such as spectral type, age, accretion activity and environment. Using the ‘Cores to Disks’ (c2d) Spitzer Legacy Program, we discovered a new population of young stellar objects (YSOs) in a region of only 0.8 deg2 in the Serpens Molecular Cloud. This sample contains 150 mid-IR bright (≥ 3 mJy at 8 μm) YSOs with infrared excess, having a broad range of SED types and luminosities. Serpens is therefore a unique target region for obtaining a complete, well-defined sample of multi-wavelength observations of young stars in a possible evolutionary sequence. Compared with other clouds such as Taurus and Chamaeleon, Serpens has an exceptionally high star-formation rate (5.7 × 10−5 M⊙ yr−1). Follow-up complimentary observations in the optical, near- and mid-infrared (Spitzer/IRS GO3) have allowed us to characterize both the central stars and the surrounding disks. The shape and slope of the mid-infrared excess provide information on the flaring geometry of the disks. The spectral features give constraints on grain growth and mineralogy, which in turn probes heating and radial mixing. The presence of PAH features traces UV radiation, whereas Hα and Brγ are used as diagnostics of accretion. Assuming that all stars within a sufficiently small region are nearly coeval, this provides direct constraints on the importance of environment and initial conditions on disk evolution. In this meeting, we have presented our latest results on this rich populations of YSOs, as detailed in Oliveira et al. (2009, 2010). We have discussed connections between the evolution of the disks and that of their harboring stars, and the processes that determine the evolutionary sequence of protoplanetary disks.

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The Initial Conditions for Planet Formation: Turbulence Driven by Hydrodynamical Instabilities in Disks around Young Stars

Publications of the Astronomical Society of the Pacific ◽

10.1088/1538-3873/aaf5ff ◽

2019 ◽

Vol 131 (1001) ◽

pp. 072001 ◽

Cited By ~ 20

Author(s):

Wladimir Lyra ◽

Orkan M. Umurhan

Keyword(s):

Planet Formation ◽

Initial Conditions ◽

Young Stars

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Discovery of a stellar companion to HD 131399A

Astronomy and Astrophysics ◽

10.1051/0004-6361/201730978 ◽

2017 ◽

Vol 608 ◽

pp. L9 ◽

Cited By ~ 1

Author(s):

A.-M. Lagrange ◽

M. Keppler ◽

H. Beust ◽

L. Rodet ◽

N. Meunier ◽

...

Keyword(s):

High Resolution ◽

Binary System ◽

Planet Formation ◽

Giant Planet ◽

Dynamical Evolution ◽

Young Stars ◽

Circumstellar Disk ◽

Mass Star ◽

Low Mass

Context. The giant exoplanets imaged on wide orbits (≥10 au) around young stars challenge the classical theories of planet formation. The presence of perturbing bodies could have played a role in the dynamical evolution of the planets once formed. Aims. We aim to search for close companions to HD 131399, a star around which a giant planet has been discovered, at a projected separation of about 80 au. The star also appears to be a member of a wide (320 au) binary system. Methods. We recorded HARPS high resolution spectra in January 2017. Results. We find that HD 131399A is probably seen close to pole-on. We discover a low mass star companion that orbits with a period of about 10 days on a misaligned orbit. Even though the companion does not have an impact on the current dynamical evolution of the planet, it could have played a role in its setting and in clearing the circumstellar disk from which the planet may originate.

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The Chemistry of Nearby Disks

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315006237 ◽

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.

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Accretion disks around young stars: the cradles of planet formation

Europhysics news ◽

10.1051/epn/2020104 ◽

2020 ◽

Vol 51 (1) ◽

pp. 29-32

Author(s):

Dmitry A. Semenov ◽

Richard D. Teague

Keyword(s):

Angular Momentum ◽

Accretion Disks ◽

Planet Formation ◽

Protoplanetary Disks ◽

Young Stars ◽

Dust Grains ◽

Gas Viscosity ◽

Disk Mass ◽

Disk Evolution ◽

Central Stars

Protoplanetary disks around young stars are the birth sites of planetary systems like our own. Disks represent the gaseous dusty matter left after the formation of their central stars. The mass and luminosity of the star, initial disk mass and angular momentum, and gas viscosity govern disk evolution and accretion. Protoplanetary disks are the cosmic nurseries where microscopic dust grains grow into pebbles, planetesimals, and planets.

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