Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Late Infall Causing Disk Misalignment and Dynamic Structures in SU Aur

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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Circumstellar disks of the most vigorously accreting young stars

Science Advances ◽

10.1126/sciadv.1500875 ◽

2016 ◽

Vol 2 (2) ◽

pp. e1500875 ◽

Cited By ~ 43

Author(s):

Hauyu Baobab Liu ◽

Michihiro Takami ◽

Tomoyuki Kudo ◽

Jun Hashimoto ◽

Ruobing Dong ◽

...

Keyword(s):

Large Scale ◽

Near Infrared ◽

Infrared Imaging ◽

Circumstellar Disks ◽

Young Stars ◽

Young Stellar Objects ◽

Stellar Objects ◽

Disk Formation ◽

Gravitational Instabilities ◽

Disk Evolution

Stars may not accumulate their mass steadily, as was previously thought, but in a series of violent events manifesting themselves as sharp stellar brightening. These events can be caused by fragmentation due to gravitational instabilities in massive gaseous disks surrounding young stars, followed by migration of dense gaseous clumps onto the star. Our high-resolution near-infrared imaging has verified the presence of the key associated features, large-scale arms and arcs surrounding four young stellar objects undergoing luminous outbursts. Our hydrodynamics simulations and radiative transfer models show that these observed structures can indeed be explained by strong gravitational instabilities occurring at the beginning of the disk formation phase. The effect of those tempestuous episodes of disk evolution on star and planet formation remains to be understood.

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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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Young stars inϵChamaleontis and their disks: disk evolution in sparse associations

Astronomy and Astrophysics ◽

10.1051/0004-6361/201118528 ◽

2012 ◽

Vol 549 ◽

pp. A15 ◽

Cited By ~ 27

Author(s):

M. Fang ◽

R. van Boekel ◽

J. Bouwman ◽

Th. Henning ◽

W. A. Lawson ◽

...

Keyword(s):

Young Stars ◽

Disk Evolution

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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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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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Three Dimensional structure and organization of diploid chromosomes by optical section microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100127608 ◽

1987 ◽

Vol 45 ◽

pp. 633-635

Author(s):

David A. Agard ◽

Yasushi Hiraoka ◽

John W. Sedat

Keyword(s):

Dimensional Space ◽

Three Dimensional ◽

Developmental State ◽

Mitotic Cell ◽

Biological Properties ◽

Dimensional Structure ◽

Specific Gene ◽

Three Dimensional Structure ◽

Complementary Techniques ◽

Dynamic Structures

In an effort to understand the complex relationship between structure and biological function within the nucleus, we have embarked on a program to examine the three-dimensional structure and organization of Drosophila melanogaster embryonic chromosomes. Our overall goal is to determine how DNA and proteins are organized into complex and highly dynamic structures (chromosomes) and how these chromosomes are arranged in three dimensional space within the cell nucleus. Futher, we hope to be able to correlate structual data with such fundamental biological properties as stage in the mitotic cell cycle, developmental state and transcription at specific gene loci.Towards this end, we have been developing methodologies for the three-dimensional analysis of non-crystalline biological specimens using optical and electron microscopy. We feel that the combination of these two complementary techniques allows an unprecedented look at the structural organization of cellular components ranging in size from 100A to 100 microns.

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Porosity evolution study in irradiated UO2 fuel based on fuel matrix swelling

Kerntechnik ◽

10.3139/124.110886 ◽

2018 ◽

Vol 83 (2) ◽

pp. 86-90 ◽

Cited By ~ 1

Author(s):

B. Roostaii ◽

H. Kazeminejad ◽

S. Khakshournia

Keyword(s):

Porosity Evolution ◽

Evolution Study

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A WIYN Lithium Survey for Young Stars in the λ Orionis Star-Forming Region

The Astronomical Journal ◽

10.1086/301075 ◽

1999 ◽

Vol 118 (5) ◽

pp. 2409-2423 ◽

Cited By ~ 44

Author(s):

Christopher J. Dolan and Robert D. Mathieu

Keyword(s):

Young Stars ◽

Star Forming

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The Observational Evidence for Accretion

Symposium - International Astronomical Union ◽

10.1017/s0074180900061805 ◽

1997 ◽

Vol 182 ◽

pp. 391-405 ◽

Cited By ~ 2

Author(s):

Lee Hartmann

Keyword(s):

Large Range ◽

Observational Evidence ◽

Young Stars ◽

Young Stellar Objects ◽

Stellar Objects ◽

T Tauri ◽

Accretion Rates ◽

Low Mass ◽

Stellar Magnetospheres ◽

Mass Ejection

Outflows from low-mass young stellar objects are thought to draw upon the energy released by accretion onto T Tauri stars. I briefly summarize the evidence for this accretion and outline present estimates of mass accretion rates. Young stars show a very large range of accretion rates, and this has important implications for both mass ejection and for the structure of stellar magnetospheres which may truncate T Tauri disks.

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