- ID:
- ivo://CDS.VizieR/J/AJ/157/196
- Title:
- Close companions around young stars
- Short Name:
- J/AJ/157/196
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiplicity is a fundamental property that is set early during stellar lifetimes, and it is a stringent probe of the physics of star formation. The distribution of close companions around young stars is still poorly constrained by observations. We present an analysis of stellar multiplicity derived from Apache Point Observatory Galactic Evolution Experiment-2 spectra obtained in targeted observations of nearby star-forming regions. This is the largest homogeneously observed sample of high-resolution spectra of young stars. We developed an autonomous method to identify double-lined spectroscopic binaries (SB2s). Out of 5007 sources spanning the mass range of ~0.05-1.5 M_{sun}_, we find 399 binaries, including both radial velocity (RV) variables and SB2s. The mass ratio distribution of SB2s is consistent with being uniform for q<0.95 with an excess of twins for q>0.95. The period distribution is consistent with what has been observed in close binaries (<10 au) in the evolved populations. Three systems are found to have q~0.1, with a companion located within the brown dwarf desert. There are no strong trends in the multiplicity fraction as a function of cluster age from 1 to 100 Myr. There is a weak dependence on stellar density, with companions being most numerous at {Sigma}_*_~30 stars/pc^-2^ and decreasing in more diffuse regions. Finally, disk-bearing sources are deficient in SB2s (but not RV variables) by a factor of ~2; this deficit is recovered by the systems without disks. This may indicate a quick dispersal of disk material in short-period equal-mass systems that is less effective in binaries with lower q.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/483/839
- Title:
- CO(2-1) maps of IRAS 18059-3211
- Short Name:
- J/A+A/483/839
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the nature of Gomez's Hamburger (IRAS 18059-3211), a nebula that has been proposed to be a post-AGB object. Such a classification has not been confirmed; instead, we argue that it will be a key object in the study of disks rotating around young stars. We present high-resolution SMA maps of CO J=2-1 (230.538GHz) in Gomez's Hamburger. The data are analyzed by means of a code that simulates the emission of a nebula showing a variety of physical conditions and kinematics. Our observations clearly show that the CO emitting gas in Gomez's Hamburger forms a spectacular disk in keplerian rotation. Model calculations undoubtedly confirm this result. The central (mainly stellar) mass is found to be high, ~4 solar masses for a distance of 500pc. The mass and (relatively low) luminosity of the source are, independent of the assumed distance, very different from those possible in evolved stars. This object is probably transitional between the pre-MS and MS phases, still showing interstellar material around the central star or stellar system.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A48
- Title:
- Compact disks CO isotopologues line fluxes
- Short Name:
- J/A+A/651/A48
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- ALMA disk surveys have shown that a large fraction of observed protoplanetary disks in nearby Star-Forming Regions (SFRs) are fainter than expected in CO isotopologue emission. Disks not detected in 13CO line emission are also faint and often unresolved in the continuum emission at an angular resolution of around 0.2 arcseconds. Focusing on the Lupus SFR, the aim of this work is to investigate whether this population comprises radially extended and low mass disks - as commonly assumed so far - or if it is of intrinsically radially compact disks, an interpretation that we propose in this paper. The latter scenario was already proposed for individual sources or small samples of disks, while this work targets a large population of disks in a single young SFR for which statistical arguments can be made. A new grid of physical-chemical models of compact disks has been run with the physical-chemical code DALI in order to cover a region of the parameter space that had not been explored before with this code. Such models have been compared with ^12^CO and ^13^CO ALMA observations of faint disks in the Lupus SFR. The simulated integrated continuum and CO isotopologue fluxes of the new grid of compact models are reported. Lupus disks that are not detected in ^13^CO emission and with faint or undetected 12CO emission are consistent with compact disk models. For disks with a limited radial extent, the emission of CO isotopologues is mostly optically thick and it scales with the surface area: i.e., it is fainter for smaller objects. The fraction of compact disks is potentially between roughly 50% and 60% of the entire Lupus sample. Deeper observations of ^12^CO and ^13^CO at a moderate angular resolution will allow us to distinguish whether faint disks are intrinsically compact, or if they are extended but faint, without the need of resolving them. If the fainter end of the disk population observed by ALMA disk surveys is consistent with such objects being very compact, this will either create a tension with viscous spreading or require MHD winds or external processes to truncate the disks.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A46
- Title:
- Compiled photometry for Cham I and II members
- Short Name:
- J/A+A/551/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a proper motion study aiming at providing further evidence on the origin of the proposed stellar members of the Chamaeleon I and II clouds and to identify interlopers from the foreground young clusters {epsilon} Cha and {eta} Cha. We compiled lists of spectroscopically confirmed members of the four associations, and of background objects in the same line of sight. Using Virtual Observatory tools, we cross-matched these lists with the UCAC3 (Cat. I/315) catalogue to get proper motions for the objects. In the vector point diagram, we identified the different moving groups, and used this information to study the membership of proposed candidate members of the associations from the literature. For those objects with available radial velocities, we computed their Galactic space velocities. We compiled photometry from public data archives and from the literature for the Cha I and II objects. We looked for correlations between the properties of the objects and their proper motions.
- ID:
- ivo://CDS.VizieR/J/ApJS/156/169
- Title:
- Confirmed class 0 sources list
- Short Name:
- J/ApJS/156/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We searched the literature to obtain a complete list of known Class 0 sources. A list of 95 confirmed or candidate objects was compiled. To the best of our knowledge, all published broadband observations from 1{mu}m to 3.5mm have been collected and are assembled in a catalog. These data were used to determine physical properties (T_bol_, L_bol_, L_smm_/L_bol_, M_env_) and for a uniform classification. Fifty sources possess sufficient observational data and are classified as Class 0 or Class 0/1 objects. The source properties are compared with different evolutionary models to infer ages and masses, and their correlations are investigated. About 25% of the sources are found to be in a quiet accretion phase or possess a significantly different time evolution of the accretion rate than the average. In Taurus, with its isolated star formation mode, this seems especially to be the case.
- ID:
- ivo://CDS.VizieR/J/A+A/474/891
- Title:
- 13CO observations of YSOs in South Gal. plane
- Short Name:
- J/A+A/474/891
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Red MSX Source (RMS) survey is an ongoing multi-wavelength observational programme designed to return a large, well-selected sample of massive young stellar objects (MYSOs). We have identified ~2000 MYSOs candidates located within our Galaxy by comparing the colours of MSX and 2MASS point sources to those of known MYSOs. The aim of our follow-up observations is to identify other contaminating objects such as ultra compact (UC) HII regions, evolved stars and planetary nebulae (PNe) and distinguish between genuine MYSOs and nearby low-mass YSOs. A critical part of our follow-up programme is to conduct ^13^CO molecular line observations in order to determine kinematic distances to all of our MYSO candidates. These distances will be used in combination with far-IR and (sub)millimetre fluxes to determine bolometric luminosities which will allow us to identify and remove nearby low-mass YSOs. In addition these molecular line observations will help in identifying evolved stars which are weak CO emitters. We have used the 22m Mopra telescope, the 15m JCMT and the 20m Onsala telescope to conduct molecular line observations towards 854 MYSOs candidates located in the 3rd and 4th quadrants. These observations have been made at the J=1-0 (Mopra and Onsala) and J=2-1 (JCMT) rotational transition frequency of ^13^CO molecules and have a spatial resolution of ~20"-40", a sensitivity of T_A_^*^~0.1K and a velocity resolution of ~0.2km/s.
- ID:
- ivo://CDS.VizieR/J/A+A/500/1045
- Title:
- Cool stars and brown dwarfs in Lupus clouds
- Short Name:
- J/A+A/500/1045
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most studies of the stellar and substellar populations of star-forming regions rely on using the signatures of accretion, outflows, disks, or activity characterizing the early stages of stellar evolution. However, these signatures rapidly decay with time. We present the results of a wide-area study of the stellar population of clouds in the Lupus star-forming region. When combined with 2MASS photometry, our data allow us to fit the spectral energy distributions of over 150000 sources and identify possible new members based on their photospheric fluxes, independent of any display of the signposts of youth.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A11
- Title:
- Corona Australis ALMA and X-Shooter data
- Short Name:
- J/A+A/626/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, the disk populations in a number of young star-forming regions have been surveyed with the Atacama Large Millimeter/submillimeter Array (ALMA). Understanding the disk properties and their correlation with the properties of the central star is critical to understanding planet formation. In particular, a decrease of the average measured disk dust mass with the age of the region has been observed, consistent with grain growth and disk dissipation. We aim to compare the general properties of disks and their host stars in the nearby (d=160pc) Corona Australis (CrA) star forming region to those of the disks and stars in other regions. We conducted high-sensitivity continuum ALMA observations of 43 Class II young stellar objects in CrA at 1.3mm (230GHz). The typical spatial resolution is 0.3''. The continuum fluxes ar e used to estimate the dust masses of the disks, and a survival analysis is performed to estimate the average dust mass. We also obtained new VLT/X-Shooter spectra for 12 of the objects in our sample for which spectral type (SpT) information was missing. Twenty-four disks were detected, and stringent limits have been put on the average dust mass of the nondetections. Taking into account the upper limits, the average disk mass in CrA is 6+/-3M_{sun}_. This value is significantly lower than that of disks in other young (1-3Myr) star forming regions (Lupus, Taurus, Chamaeleon I, and Ophiuchus) and appears to be consistent with the average disk mass of the 5-10Myr-old Upper Sco. The position of the stars in our sample on the Herzsprung-Russel diagram however seems to confirm that CrA has an age similar to Lupus. Neither external photoevaporation nor a lower-than-usual stellar mass distribution can explain the low disk masses. On the other hand, a low-mass disk population could be explained if the disks were small, which could happen if the parent cloud had a low temperature or intrinsic angular momentum, or if the angular momentum of the cloud were removed by some physical mechanism such as magnetic braking. Even in detected disks, none show clear substructures or cavities. Our results suggest that in order to fully explain and understand the dust mass distribution of protoplanetary disks and their evolution, it may also be necessary to take into consideration the initial conditions of star- and disk-formation process. These conditions at the very beginning may potentially vary from region to region, and could play a crucial role in planet formation and evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/589/A60
- Title:
- CO, SO and H_2_CO images of AB Aur
- Short Name:
- J/A+A/589/A60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transitional disks are structures of dust and gas around young stars with large inner cavities in which planet formation may occur. Lopsided dust distributions are observed in the dust continuum emission at millimeter wavelengths. These asymmetrical structures can be explained as being the result of an enhanced gas density vortex where the dust is trapped, potentially promoting the rapid growth to the planetesimal scale. AB Aur hosts a transitional disk with a clear horseshoe morphology which strongly suggests the presence of a dust trap. Our goal is to investigate its formation and the possible effects on the gas chemistry. We used the NOrthern Extended Millimeter Array (NOEMA) interferometer to image the 1mm continuum dust emission and the ^13^CO J=2->1, C^18^O J=2->1, SO J=5_6_->4_5_, and H_2_CO J=3_03_->2_02_. rotational lines.
- ID:
- ivo://CDS.VizieR/J/ApJS/160/319
- Title:
- COUP: observations and source lists
- Short Name:
- J/ApJS/160/319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a description of the data reduction methods and the derived catalog of more than 1600 X-ray point sources from the exceptionally deep 2003 January Chandra X-Ray Observatory (Chandra) observation of the Orion Nebula Cluster and embedded populations around OMC-1. The observation was obtained with Chandra's Advanced CCD Imaging Spectrometer (ACIS) and has been nicknamed the Chandra Orion Ultradeep Project (COUP). With an 838ks exposure made over a continuous period of 13.2 days, the COUP observation provides the most uniform and comprehensive data set on the X-ray emission of normal stars ever obtained in the history of X-ray astronomy.
