- ID:
- ivo://CDS.VizieR/J/ApJS/245/13
- Title:
- CDIPS. I. LCs from TESS sectors 6 and 7
- Short Name:
- J/ApJS/245/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) is providing precise time-series photometry for most star clusters in the solar neighborhood. Using the TESS images, we have begun a Cluster Difference Imaging Photometric Survey, in which we are focusing both on stars that are candidate cluster members and on stars that show indications of youth. Our aims are to discover giant transiting planets with known ages, and to provide light curves suitable for studies in stellar astrophysics. For this work, we made 159343 light curves of candidate young stars, across 596 distinct clusters. Each light curve represents between 20 and 25 days of observations of a star brighter than G_Rp_=16, with 30-minute sampling. We describe the image-subtraction and time-series analysis techniques we used to create the light curves, which have noise properties that agree with theoretical expectations. We also comment on the possible utility of the light-curve sample for studies of stellar rotation evolution and binary eccentricity damping.
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- ID:
- ivo://CDS.VizieR/J/ApJS/215/24
- Title:
- Census of blue stars in SDSS DR8
- Short Name:
- J/ApJS/215/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a census of the 12060 spectra of blue objects ((g-r)_0_<-0.25) in the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8). As part of the data release, all of the spectra were cross-correlated with 48 template spectra of stars, galaxies, and QSOs to determine the best match. We compared the blue spectra by eye to the templates assigned in SDSS DR8. 10856 of the objects matched their assigned template, 170 could not be classified due to low signal-to-noise ratio, and 1034 were given new classifications. We identify 7458 DA white dwarfs, 1145 DB white dwarfs, 273 rarer white dwarfs (including carbon, DZ, DQ, and magnetic), 294 subdwarf O stars, 648 subdwarf B stars, 679 blue horizontal branch stars, 1026 blue stragglers, 13 cataclysmic variables, 129 white dwarf-M dwarf binaries, 36 objects with spectra similar to DO white dwarfs, 179, quasi-stellar objects (QSOs), and 10 galaxies. We provide two tables of these objects, sample spectra that match the templates, figures showing all of the spectra that were grouped by eye, and diagnostic plots that show the positions, colors, apparent magnitudes, proper motions, etc., for each classification.
- ID:
- ivo://CDS.VizieR/J/ApJS/219/19
- Title:
- Census of nearby white dwarfs from SUPERBLINK
- Short Name:
- J/ApJS/219/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed description of the physical properties of our current census of white dwarfs within 40pc of the Sun, based on an exhaustive spectroscopic survey of northern hemisphere candidates from the SUPERBLINK proper motion database. Our method for selecting white dwarf candidates is based on a combination of theoretical color-magnitude relations and reduced proper motion diagrams. We reported in an earlier publication the discovery of nearly 200 new white dwarfs, and we present here the discovery of an additional 133 new white dwarfs, among which we identify 96 DA, 3 DB, 24 DC, 3 DQ, and 7 DZ stars. We further identify 178 white dwarfs that lie within 40pc of the Sun, representing a 40% increase of the current census, which now includes 492 objects. We estimate the completeness of our survey at between 66% and 78%, allowing for uncertainties in the distance estimates. We also perform a homogeneous model atmosphere analysis of this 40pc sample and find a large fraction of massive white dwarfs, indicating that we are successfully recovering the more massive, and less luminous objects often missed in other surveys. We also show that the 40pc sample is dominated by cool and old white dwarfs, which populate the faint end of the luminosity function, although trigonometric parallaxes will be needed to shape this part of the luminosity function more accurately. Finally, we identify 4 probable members of the 20pc sample, 4 suspected double degenerate binaries, and we also report the discovery of two new ZZ Ceti pulsators.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/2238
- Title:
- Cepheids in open clusters
- Short Name:
- J/MNRAS/434/2238
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cepheids in open clusters (cluster Cepheids: CCs) are of great importance as zero-point calibrators of the Galactic Cepheid period-luminosity relationship (PLR). We perform an 8-dimensional all-sky census that aims to identify new bona-fide CCs and provide a ranking of membership confidence for known CC candidates according to membership probabilities. The probabilities are computed for combinations of known Galactic open clusters and classical Cepheid candidates, based on spatial, kinematic, and population-specific membership constraints. Data employed in this analysis are taken largely from published literature and supplemented by a year-round observing program on both hemispheres dedicated to determining systemic radial velocities of Cepheids. In total, we find 23 bona-fide CCs, 5 of which are candidates identified for the first time, including an overtone-Cepheid member in NGC 129. We discuss a subset of CC candidates in detail, some of which have been previously mentioned in the literature. Our results indicate unlikely membership for 7 Cepheids that have been previously discussed in terms of cluster membership. We furthermore revisit the Galactic PLR using our bona fide CC sample and obtain a result consistent with the recent calibration by Turner (2010). However, our calibration remains limited mainly by cluster uncertainties and the small number of long-period calibrators. In the near future, Gaia will enable our study to be carried out in much greater detail and accuracy, thanks to data homogeneity and greater levels of completeness.
- ID:
- ivo://CDS.VizieR/J/MNRAS/349/1069
- Title:
- Chromospherically active binaries
- Short Name:
- J/MNRAS/349/1069
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The kinematics of 237 chromospherically active binaries (CABs) were studied. The sample is heterogeneous with different orbits and physically different components from F to M spectral-type main-sequence stars to G and K giants and supergiants. The computed U, V, W space velocities indicate that the sample is also heterogeneous in velocity space.
- 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/650/A156
- Title:
- Cluster formation toward Be87/ON2. I.
- Short Name:
- J/A+A/650/A156
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Disentangling line-of-sight alignments of young stellar populations is crucial for observational studies of star-forming complexes. This task is particularly problematic in a Cygnus-X subregion where several components, located at different distances, overlap: the Berkeley 87 young massive cluster, the poorly known [DB2001] Cl05 embedded cluster, and the ON2 star-forming complex, which in turn is composed of several HII regions. We provide a methodology for building an exhaustive census of young objects that can consistently treat large differences in extinction and distance. OMEGA2000 near-infrared observations of the Berkeley 87 / ON2 field were merged with archival data from Gaia, Chandra, Spitzer, and Herschel, and with cross-identifications from the literature. To address the incompleteness effects and selection biases that arise from the line-of-sight overlap, we adapted existing methods for extinction estimation and young object classification. We also defined the intrinsic reddening index, R_int_, a new tool for separating intrinsically red sources from those whose infrared color excess is caused by extinction. Finally, we introduce a new method for finding young stellar objects based on R_int_. We find 571 objects whose classification is related to recent or ongoing star formation. Together with other point sources with individual estimates of distance or extinction, we compile a catalog of 3005 objects to be used for further membership work. A new distance for Berkeley 87, (1673+/-17)pc, is estimated as a median of 13 spectroscopic members with accurate Gaia EDR3 parallaxes. The flexibility of our approach, especially regarding the R_int_ definition, allows overcoming photometric biases caused by large variations in extinction and distance, in order to obtain homogeneous catalogs of young sources. The multiwavelength census that results from applying our methods to the Berkeley 87 / ON2 field will serve as a basis for disentangling the overlapped populations.
118. Clusterix 2.0
- ID:
- ivo://CDS.VizieR/J/MNRAS/492/5811
- Title:
- Clusterix 2.0
- Short Name:
- J/MNRAS/492/5811
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Clusterix 2.0 is a web-based, Virtual Observatory compliant, interactive tool for the determination of membership probabilities in stellar clusters based on proper-motion data using a fully non-parametric method. In an area occupied by a cluster, the frequency function is made up of two contributions: cluster and field stars. The tool performs an empirical determination of the frequency functions from the vector point diagram without relying on any previous assumption about their profiles. Clusterix 2.0 allows us to search the appropriate spatial areas in an interactive way until an optimal separation of the two populations is obtained. Several parameters can be adjusted to make the calculation computationally feasible without interfering with the quality of the results. The system offers the possibility to query different catalogues, such as Gaia, or upload a user's own data. The results of the membership determination can be sent via Simple Application Messaging Protocol (SAMP) to Virtual Observatory (VO) tools such as Tool for OPerations on Catalogues And Tables (TOPCAT). We apply Clusterix 2.0 to several open clusters with different properties and environments to show the capabilities of the tool: an area of five degrees radius around NGC 2682 (M67), an old, well-known cluster; a young cluster NGC 2516 with a striking elongated structure extended up to four degrees; NGC 1750 and NGC 1758, a pair of partly overlapping clusters; the area of NGC 1817, where we confirm a little-known cluster, Juchert 23; and an area with many clusters, where we disentangle two overlapping clusters situated where only one was previously known: Ruprecht 26 and the new Clusterix 1.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/207
- Title:
- Cold stellar stream orbit fit
- Short Name:
- J/ApJ/697/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use velocity and metallicity information from Sloan Digital Sky Survey and Sloan Extension for Galactic Understanding and Exploration stellar spectroscopy to fit an orbit to the narrow 63{deg} stellar stream of Grillmair and Dionatos (GD; 2006ApJ...643L..17G). The stars in the stream have a retrograde orbit with eccentricity e=0.33 (perigalacticon of 14.4kpc and apogalacticon of 28.7kpc) and inclination approximately i~35{deg}. In the region of the orbit which is detected, it has a distance of about 7-11kpc from the Sun. Assuming a standard disk plus bulge and logarithmic halo potential for the Milky Way stars plus dark matter, the stream stars are moving with a large space velocity of approximately 276km/s at perigalacticon. Using this stream alone, we are unable to determine if the dark matter halo is oblate or prolate. The metallicity of the stream is [Fe/H]=-2.1+/-0.1. Observed proper motions for individual stream members above the main sequence turnoff are consistent with the derived orbit. None of the known globular clusters in the Milky Way have positions, radial velocities, and metallicities that are consistent with being the progenitor of the GD-1 stream.
- ID:
- ivo://CDS.VizieR/J/ApJ/877/12
- Title:
- Coma Ber and a Neighbor Stellar Group tidal tails
- Short Name:
- J/ApJ/877/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of tidal structures around the intermediate-aged (~700-800Myr), nearby (~85pc) star cluster Coma Berenices. The spatial and kinematic grouping of stars is determined with the Gaia DR2 parallax and proper motion data, by a clustering analysis tool, StarGO, to map 5D parameters (X, Y, Z, {mu}_{alpha}*cos{delta}, {mu}_{delta}_) onto a 2D neural network. A leading and a trailing tails, each with an extension of ~50pc are revealed for the first time around this disrupting star cluster. The cluster members, totaling to ~115^+5^_-3_M_{sun}_, are clearly mass segregated, and exhibit a flat mass function with {alpha}~0.79+/-0.16, in the sense of dN/dm{prop.to}m^-{alpha}^, where N is the number of member stars and m is stellar mass, in the mass range of m=0.25-2.51M_{sun}_. Within the tidal radius of ~6.9pc, there are 77 member candidates with an average position, i.e., as the cluster center, of RA=186.8110{deg}, and DE=25.8112{deg}, and an average distance of 85.8pc. Additional 120 member candidates reside in the tidal structures, i.e., outnumbering those in the cluster core. The expansion of escaping members lead to an anisotropy in the velocity field of the tidal tails. Our analysis also serendipitously uncovers an adjacent stellar group, part of which has been cataloged in the literature. We identify 218 member candidates, 10 times more than previously known. This star group is some 65pc away from, and ~400Myr younger than, Coma Ber, but is already at the final stage of disruption.
