- ID:
- ivo://CDS.VizieR/J/AJ/119/3026
- Title:
- Circumstellar disk candidates in Orion
- Short Name:
- J/AJ/119/3026
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an optical study of four 45'x45' fields centered ~0.5{deg} east, west, north, and south of the Orion Nebula Cluster center. We have measured V and I_C_ photometry for ~5000 stars, and U photometry for ~1600 of these. We have obtained spectral classifications for ~300 of the stars with UVI_C_ photometry plus an additional ~200 stars located outside the area of our photometric survey. Dereddened photometry allows us to investigate the evidence for circumstellar accretion disks from excess emission at ultraviolet wavelengths, as well as the mass and age distributions of our sample. We find ~230 active accretion disk candidates and estimate the accretion disk fraction at >~40%. We use the magnitude of the ultraviolet excess to infer disk accretion rates. The mass accretion rate (dM/dt) decreases slowly with age over the limited age range spanned by our data, 1-3Myr, and increases slowly with mass over the limited mass range 0.2-1.2 M_{sun}_.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/156/75
- Title:
- Circumstellar disks in the Upper Sco association
- Short Name:
- J/AJ/156/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a survey for new members of the Upper Sco association that have circumstellar disks using mid-infrared photometry from the Wide-field Infrared Survey Explorer (WISE). Through optical and near-infrared spectroscopy, we have confirmed 185 candidates as likely members of Upper Sco with spectral types ranging from mid-K to M9. They comprise ~36% of the known disk-bearing members of the association. We also have compiled all available mid-infrared photometry from WISE and the Spitzer Space Telescope for the known members of Upper Sco, resulting in a catalog of data for 1608 objects. We have used these data to identify the members that exhibit excess emission from disks and we have classified the evolutionary stages of those disks with criteria similar to those applied in our previous studies of Taurus and Upper Sco. Among 484 members with excesses in at least one band (excluding five Be stars), we classify 296 disks as full, 66 as evolved, 19 as transitional, 22 as evolved or transitional, and 81 as evolved transitional or debris. Many of these disks have not been previously reported, including 129 full disks and 50 disks that are at more advanced evolutionary stages.
- ID:
- ivo://CDS.VizieR/J/A+A/441/195
- Title:
- Circumstellar disks in Trapezium cluster
- Short Name:
- J/A+A/441/195
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present results on the size distribution of circumstellar disks in the Trapezium cluster as measured from HST/WFPC2 data. Direct diameter measurements of a sample of 135 bright proplyds and 14 silhouettes disks suggest that there is a single population of disks well characterized by a power-law distribution with an exponent of -1.9+/-0.3 between disk diameters 100-400AU. For the stellar mass sampled (from late G to late M stars) we find no obvious correlation between disk diameter and stellar mass. We also find that there is no obvious correlation between disk diameter and the projected distance to the ionizing Trapezium OB stars. We estimate that about 40% of the disks in the Trapezium have radius larger than 50AU. We suggest that the origin of the Solar system's (Kuiper belt) outer edge is likely to be due to the star formation environment and disk destruction processes (photo-evaporation, collisions) present in the stellar cluster on which the Sun was probably formed. Finally, we identified a previously unknown proplyd and named it 266-557, following convention.
- ID:
- ivo://CDS.VizieR/J/A+A/378/116
- Title:
- Classification and vsini of Vega-type and PMS stars
- Short Name:
- J/A+A/378/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table1.dat contains the log of the spectroscopic observations of the stars in the EXPORT sample taken with the Isaac Newton Telescope during the 1998 International Time Campaigns at the Canary Islands' Observatories. File table2.dat contains the log of the spectroscopic observations of the stars in the EXPORT sample taken with the William Herschel Telescope during the 1998 International Time Campaigns at the Canary Islands' Observatories. File table6.dat contains the results of the spectral classification and the projected rotational velocities for the stars in the EXPORT sample with comparisons with results from previous work.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A50
- Title:
- Classification of stellar spectra 644-681nm
- Short Name:
- J/A+A/566/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of spectral diagnostics available from optical spectra with R=17000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the {gamma} Vel young cluster, with the purpose of classifying these stars and finding their fundamental parameters. We define several spectroscopic indices, sampling the amplitude of TiO bands, the H{alpha} line core and wings, and temperature- and gravity-sensitive sets of lines, each useful as a Teff or logg indicator over a limited range of stellar spectral types. H{alpha} line indices are also useful as chromospheric activity or accretion indicators. Furthermore, we use all indices to define additional global Teff- and logg-sensitive indices {tau} and {gamma}, valid for the entire range of types in the observed sample.
- 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.
- 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.
