- ID:
- ivo://CDS.VizieR/J/MNRAS/413/1581
- Title:
- Candidate subdwarfs and white dwarfs
- Short Name:
- J/MNRAS/413/1581
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry from the Two-Micron All-Sky Survey (2MASS), United States Naval Observatory CCD Astrograph Catalog (UCAC3) and SuperCosmos catalogues, together with proper motions from the Tycho-2, Kharkiv Proper Motions (XPM) and UCAC3 catalogues, is used to select all-sky samples of 28 candidate white dwarfs, 1826 evolved and 7641 unevolved subdwarfs for R from 9-17mag. The samples are separated from main-sequence stars with an admixture of less than 10 per cent, owing to an analysis of the distribution of the stars in colour index versus reduced proper-motion diagrams for various latitudes using related Monte Carlo simulations. It is shown that the XPM and UCAC3 catalogues have the same level of proper-motion accuracy. Most of the selected stars have at least six-band photometry. This allows us to eliminate some admixtures and reveal some binaries. Empirical calibrations of absolute magnitude versus colour index and reduced proper motion for Hipparcos stars give us distances and a three-dimensional (3D) distribution for all the selected stars. It is shown that the subdwarf samples are almost complete for the Tycho-2 stars, i.e. to 11mag or 150pc from the Sun. For fainter stars from the XPM and UCAC3 catalogues, the subdwarf samples are complete only to 20-60 per cent because of the selection method and incompleteness of the catalogues.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/628/A102
- Title:
- Carbon-rich (DQ) white dwarfs in SDSS
- Short Name:
- J/A+A/628/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Among the spectroscopically identified white dwarfs, a fraction smaller than 2% have spectra dominated by carbon lines, mainly molecular C_2_, but also in a smaller group by CI and CII lines. These are together called DQ white dwarfs. We derive atmospheric parameters Teff, logg, and carbon abundances for a large sample of these stars and discuss implications for their spectral evolution. Sloan Digital Sky Survey spectra and ugriz photometry were used, together with Gaia Data Release 2 parallaxes and G band photometry. These were fitted to synthetic spectra and theoretical photometry derived from model atmospheres. We found that the DQs hotter than Teff ~10000K have masses ~0.4M_{sun}_ larger than the classical DQ, which have masses typical for the majority of white dwarfs (~0.6M_{sun}_). We found some evidence that the peculiar DQ below 10000K also have significantly larger masses and may thus be the descendants of the hot and warm DQs above 10000K. A significant fraction of the hotter objects with Teff>14500K have atmospheres dominated by carbon.
- ID:
- ivo://CDS.VizieR/J/ApJ/765/12
- Title:
- Carbon stars and DQ white dwarfs from SDSS-DR7+DR8
- Short Name:
- J/ApJ/765/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Among stars showing carbon molecular bands (C stars), the main-sequence dwarfs, likely in post-mass transfer binaries, are numerically dominant in the Galaxy. Via spectroscopic selection from the Sloan Digital Sky Survey, we retrieve 1220 high galactic latitude C stars, ~5 times more than previously known, including a wider variety than past techniques such as color or grism selection have netted, and additionally yielding 167 DQ white dwarfs. Of the C stars with proper motion measurements, we identify 69% clearly as dwarfs (dCs), while ~7% are giants. The dCs likely span absolute magnitudes M_i_ from ~6.5 to 10.5. "G-type" dC stars with weak CN and relatively blue colors are probably the most massive dCs still cool enough to show C_2_bands. We report Balmer emission in 22 dCs, none of which are G-types. We find 8 new DA/dC stars in composite spectrum binaries, quadrupling the total sample of these "smoking guns" for AGB binary mass transfer. Eleven very red C stars with strong red CN bands appear to be "N"-type AGB stars at large Galactocentric distances, one likely a new discovery in the dIrr galaxy Leo A. Two such stars within 30' of each other may trace a previously unidentified dwarf galaxy or tidal stream at ~40 kpc. We explore the multiwavelength properties of the sample and report the first X-ray detection of a dC star, which shows strong Balmer emission. Our own spectroscopic survey additionally provides the dC surface density from a complete sample of dwarfs limited by magnitude, color, and proper motion.
- ID:
- ivo://CDS.VizieR/J/ApJ/607/426
- Title:
- Catalog of white dwarfs in SDSS-DR1
- Short Name:
- J/ApJ/607/426
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the full spectroscopic white dwarf and hot subdwarf sample from the Sloan Digital Sky Survey (SDSS) First Data Release, DR1. We find 2551 white dwarf stars of various types, 240 hot subdwarf stars, and an additional 144 objects we have identified as uncertain white dwarf stars. Of the white dwarf stars, 1888 are nonmagnetic DA types and 171 are nonmagnetic DBs. The remaining (492) objects consist of all different types of white dwarf stars: DO, DQ, DC, DH, DZ, hybrid stars such as DAB, etc., and those with nondegenerate companions. We fit the DA and DB spectra with a grid of models to determine the T_eff_ and logg for each object. For all objects, we provide coordinates, proper motions, SDSS photometric magnitudes, and enough information to retrieve the spectrum/image from the SDSS public database. This catalog nearly doubles the known sample of spectroscopically identified white dwarf stars. In the DR1 imaged area of the sky, we increase the known sample of white dwarf stars by a factor of 8.5. We also comment on several particularly interesting objects in this sample.
- ID:
- ivo://CDS.VizieR/J/A+A/316/147
- Title:
- Catalogue of ROSAT White Dwarfs
- Short Name:
- J/A+A/316/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table1 lists all white dwarf stars, both previously-catalogued and newly discovered, which have been detected in the ROSAT All-Sky Survey. The positions and count rates of the X-ray sources associated with each star are given, as well as spectral types and other star names for those stars which have been previously catalogued. Table2 lists distances estimated via Balmer line profile fitting, corrected (for IS absorption) X-ray luminosities, and each star's contribution to the X-ray luminosity function for all DA white dwarfs which were detected in the ROSAT All-Sky Survey.
- ID:
- ivo://CDS.VizieR/J/MNRAS/508/3877
- Title:
- Catalogue of white dwarfs in Gaia EDR3
- Short Name:
- J/MNRAS/508/3877
- Date:
- 06 Dec 2021 19:56:36
- Publisher:
- CDS
- Description:
- We present a catalogue of white dwarf candidates selected from Gaia Early Data Release 3 (EDR3). We applied several selection criteria in absolute magnitude, colour, and Gaia quality flags to remove objects with unreliable measurements while preserving most stars compatible with the white dwarf locus in the Hertzsprung-Russell diagram. We then used a sample of over 30000 spectroscopically confirmed white dwarfs and contaminants from the Sloan Digital Sky Survey (SDSS) to map the distribution of these objects in the Gaia absolute magnitude-colour space. Finally, we adopt the same method presented in our previous work on Gaia Data Release 2 (DR2) to calculate a probability of being a white dwarf (P_WD_) for ~=1.3 million sources that passed our quality selection. The P_WD_ values can be used to select a sample of \simeq 359000 high-confidence white dwarf candidates. We calculated stellar parameters (effective temperature, surface gravity, and mass) for all these stars by fitting Gaia astrometry and photometry with synthetic pure-H, pure-He, and mixed H-He atmospheric models. We estimate an upper limit of 93 per cent for the overall completeness of our catalogue for white dwarfs with G>=20mag and effective temperature (T_eff_)>7000K, at high Galactic latitudes (|b|>20{deg}). Alongside the main catalogue we include a reduced proper motion extension containing ~=10200 white dwarf candidates with unreliable parallax measurements that could, however, be identified on the basis of their proper motion. We also performed a cross-match of our catalogues with SDSS Data Release 16 (DR16) spectroscopy and provide spectral classification based on visual inspection for all resulting matches.
- 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/449/574
- Title:
- Circumstellar discs at white dwarfs
- Short Name:
- J/MNRAS/449/574
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarfs whose atmospheres are polluted by terrestrial-like planetary debris have become a powerful and unique tool to study evolved planetary systems. This paper presents results for an unbiased Spitzer Infrared Array Camera search for circumstellar dust orbiting a homogeneous and well-defined sample of 134 single white dwarfs. The stars were selected without regard to atmospheric metal content but were chosen to have (1) hydrogen-rich atmospheres, (2) 17000<Teff<25000K and correspondingly young post-main-sequence ages of 15-270Myr, and (3) sufficient far-ultraviolet brightness for a corresponding Hubble Space Telescope COS snapshot. Five white dwarfs were found to host an infrared bright dust disc, three previously known, and two reported here for the first time, yielding a nominal 3.7^+2.4^_-1.0_ percent of white dwarfs in this post-main-sequence age range with detectable circumstellar dust. Remarkably, the complementary Hubble observations indicate that a fraction of 27 percent show metals in their photosphere that can only be explained with ongoing accretion from circumstellar material, indicating that nearly 90 percent of discs escape detection in the infrared, likely due to small emitting surface area. This paper also presents the distribution of disc fractional luminosity as a function of cooling age for all known dusty white dwarfs, suggesting possible disc evolution scenarios and indicating an undetected population of circumstellar discs.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1674
- Title:
- Close binary systems from SDSS DR4
- Short Name:
- J/AJ/131/1674
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic sample of 746 detached close binary systems from the Sloan Digital Sky Survey (SDSS) Fourth Data Release (2006ApJS..162...38A). The majority of these binaries consist of a white dwarf primary and a low-mass secondary (typically M dwarf) companion. We have determined the temperature and gravity for 496 of the white dwarf primaries and the spectral type and magnetic activity properties for 661 of the low-mass secondaries. We have estimated the distances for each of the white dwarf-main-sequence star binaries and use white dwarf evolutionary grids to establish the age of each binary system from the white dwarf cooling times.
