- ID:
- ivo://CDS.VizieR/J/ApJ/652/1554
- Title:
- Iron in hot DA white dwarfs
- Short Name:
- J/ApJ/652/1554
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the iron abundance pattern in hot, hydrogen-rich (DA) white dwarfs. The study is based on new and archival far-ultraviolet spectroscopy of a sample of white dwarfs in the temperature range 30000K<=Teff<=64000K. The spectra obtained with the Far Ultraviolet Spectroscopic Explorer, along with spectra obtained with the Hubble Space Telescope Imaging Spectrograph and the International Ultraviolet Explorer, sample FeIII-FeVI absorption lines, enabling a detailed iron abundance analysis over a wider range of effective temperatures than previously afforded.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/657/1013
- Title:
- IR photometry of 2MASS/Spitzer white dwarfs
- Short Name:
- J/ApJ/657/1013
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We review the available near- and mid-infrared photometry for white dwarfs obtained from the Two Micron All Sky Survey (2MASS) and by the Spitzer Space Telescope. Both data sets have recently been used to seek white dwarfs with infrared excesses due to the presence of unresolved companions or circumstellar disks, and also to derive the atmospheric parameters of cool white dwarfs. We first attempt to evaluate the reliability of the 2MASS photometry by comparing it with an independent set of published JHK CIT magnitudes for 160 cool white dwarf stars, and also by comparing the data with the predictions of detailed model atmosphere calculations. The possibility of using 2MASS to identify unresolved M dwarf companions or circumstellar disks is then discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/420/507
- Title:
- Isolated massive white dwarfs catalog
- Short Name:
- J/A+A/420/507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the catalogue of 112 massive isolated white dwarfs, both magnetic and nonmagnetic, with masses M>0.8M_{sun}_. Mass determinations and other parameters of white dwarfs were compiled from the available literature.
- ID:
- ivo://CDS.VizieR/J/ApJS/119/207
- Title:
- IUE echelle spectra of hot white dwarfs
- Short Name:
- J/ApJS/119/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper summarizes the results obtained from a comprehensive analysis of all of the SWP echelle spectra of the white dwarf stars contained in the IUE Final Archive. A total of 209 NEWSIPS spectra of 55 degenerate stars of various types have been systematically reduced and analyzed. These include, in addition to conventional white dwarfs, several examples of the hot planetary nebula central stars such as NGC 246, which represent the initial stages of He-rich degenerate evolution. A representative summary of the stellar, circumstellar, and interstellar features found to be present in these spectra is presented. For 33 of the 55 stars, multiple spectra of sufficient quality exist so that co-added spectra with improved signal-to-noise ratio can be constructed. Much previously unrecognized detail and many new features are evident in these data. In addition, it was found necessary to apply several corrections to the NEWSIPS extracted spectra. These corrections, involving the wavelength scale and flux uncertainty vector, are described.
- ID:
- ivo://CDS.VizieR/J/ApJS/147/145
- Title:
- IUE low-dispersion spectra of white dwarfs
- Short Name:
- J/ApJS/147/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have produced an archive of the ultraviolet low-dispersion spectra for the full set of white dwarf stars observed with the International Ultraviolet Explorer (IUE) satellite over the course of its 18-yr mission. This archive contains the spectra of 322 individual degenerate stars which have been processed to optimize the signal-to- noise for each star. In particular, all spectra have been corrected for residual temporal and thermal effects and placed on the Hubble Space Telescope Faint Object Spectrograph absolute flux scale using procedures described by Massa & Fitzpatrick (2000ApJS..126..517M). Wherever possible, multiple observations of individual stars have been co-added to further enhance signal-to-noise and have been combined into a single spectrum including the full 1150 to 3150{AA} wavelength region observed by IUE. The contents of this spectral archive are described and the details of data reduction procedures are provided. The electronic files of the processed spectra are available, in FITS and ASCII formats, with the associated log file, at http://vega.lpl.arizona.edu/newsips/low/
- ID:
- ivo://CDS.VizieR/J/A+A/658/A79
- Title:
- J-PLUS white dwarf atmospheric parameters
- Short Name:
- J/A+A/658/A79
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We estimated the spectral evolution of white dwarfs with effective temperature using the Javalambre Photometric Local Universe Survey (J-PLUS) second data release (DR2), which provides 12 photometric optical passbands over 2176deg^2^. We analyzed 5926 white dwarfs with r<19.5mag in common between a white dwarf catalog defined from Gaia EDR3 and J-PLUS DR2. We performed a Bayesian analysis by comparing the observed J-PLUS photometry with theoretical models of hydrogen- and helium-dominated atmospheres. We estimated the probability distribution functions for effective temperature (Teff), surface gravity, parallax, and composition; and the probability of having a H-dominated atmosphere (p_H_) for each source. We applied a prior in parallax, using Gaia EDR3 measurements as a reference, and derived a self-consistent prior for the atmospheric composition as a function of Teff. We described the fraction of white dwarfs with a He-dominated atmosphere (f_He_) with a linear function of the effective temperature at 5000<Teff<30000K. We find f_He_=0.24+/-0.01 at Teff=10000K, a change rate along the cooling sequence of 0.14+/-0.02 per 10kK, and a minimum He-dominated fraction of 0.08+/-0.02 at the high-temperature end. We tested the obtained p_H_ by comparison with spectroscopic classifications, finding that it is reliable. We estimated the mass distribution for the 351 sources with distance d<100pc, mass M>0.45M_{sun}_, and Teff>6000K. The result for H-dominated white dwarfs agrees with previous studies, with a dominant M=0.59M_{sun}_ peak and the presence of an excess at M~0.8M_{sun}_. This high-mass excess is absent in the He-dominated distribution, which presents a single peak. The J-PLUS optical data provide a reliable statistical classification of white dwarfs into H- and He-dominated atmospheres. We find a 21+/-3% increase in the fraction of He-dominated white dwarfs from Teff=20000K to Teff=5000K.
- ID:
- ivo://CDS.VizieR/J/MNRAS/409/1470
- Title:
- Kepler compact pulsator candidates
- Short Name:
- J/MNRAS/409/1470
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the first two quarters of a survey to search for pulsations in compact stellar objects with the Kepler spacecraft. The survey sample and the various methods applied in its compilation are described, and spectroscopic observations are presented to separate the objects into accurate classes. From the Kepler photometry we clearly identify nine compact pulsators and a number of interesting binary stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/414/2860
- Title:
- Kepler compact pulsator candidates
- Short Name:
- J/MNRAS/414/2860
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the final 6 months of a survey to search for pulsations in white dwarfs (WDs) and hot subdwarf stars with the Kepler spacecraft. Spectroscopic observations are used to separate the objects into accurate classes, and we explore the physical parameters of the subdwarf B (sdB) stars and white dwarfs in the sample. From the Kepler photometry and our spectroscopic data, we find that the sample contains five new pulsators of the V1093 Her type, one AM CVn type cataclysmic variable and a number of other binary systems.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A22
- Title:
- Kinematic properties of white dwarfs
- Short Name:
- J/A+A/658/A22
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Kinematic and chemical tagging of stellar populations have both revealed much information on the past and recent history of the Milky Way, including its formation history, merger events, and mixing of populations across the Galactic disk and halo. We present the first detailed 3D kinematic analysis of a sample of 3133 white dwarfs that used Gaia astrometry plus radial velocities, which were measured either by Gaia or by ground-based spectroscopic observations. The sample includes either isolated white dwarfs that have direct radial velocity measurements, or white dwarfs that belong to common proper motion pairs that contain nondegenerate companions with available radial velocities. A subset of common proper motion pairs also have metal abundances that have been measured by large-scale spectroscopic surveys or by our own follow-up observations. We used the white dwarfs as astrophysical clocks by determining their masses and total ages through interpolation with dedicated evolutionary models. We also used the nondegenerate companions in common proper motions to chemically tag the population. Combining accurate radial velocities with Gaia astrometry and proper motions, we derived the velocity components of our sample in the Galactic rest frame and their Galactic orbital parameters. The sample is mostly located within ~300 pc from the Sun. It predominantly contains (90-95%) thin-disk stars with almost circular Galactic orbits, while the remaining 5-10% of stars have more eccentric trajectories and belong to the thick disk. We identified seven isolated white dwarfs and two common proper motion pairs as halo members. We determined the age - velocity dispersion relation for the thin-disk members, which agrees with previous results that were achieved from different white dwarf samples without published radial velocities. The age - velocity dispersion relation shows signatures of dynamical heating and saturation after 4-6 Gyr. We observed a mild anticorrelation between [Fe/H] and the radial component of the average velocity dispersion, showing that dynamical mixing of populations takes place in the Galactic disk, as was detected through the analysis of other samples of FGK stars. We have shown that a white dwarf sample with accurate 3D kinematics and well-measured chemical compositions enables a wider understanding of their population in the solar neighborhood and its connection with the Galactic chemodynamics. The legacy of existing spectroscopic surveys will be boosted by the availability of upcoming larger samples of white dwarfs and common proper motion pairs with more uniform high-quality data.
- ID:
- ivo://CDS.VizieR/J/ApJS/61/569
- Title:
- KPD UV-excess objects
- Short Name:
- J/ApJS/61/569
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey for ultraviolet-excess objects has been performed for over about 1000sq.deg of the Galactic plane. Photographic blue and ultraviolet plates were obtained to select ultraviolet-excess candidates, and spectroscopic observations were used to determine the nature of those objects. Over 70 white dwarfs and subdwarfs were identified from the survey plates, and these objects were analyzed statistically to determine scale heights and space densities. The sample was complete to B=15.3mag, with the space density of white dwarfs for Mv<12.25 equal to 0.72+/-0.25 per 1000pc^3^, slightly higher than that from the Palomar-Green survey. The average absolute magnitude determined for both the subdwarf O and the subdwarf B stars was considerably fainter than previous determinations, while the scale height for the subdwarfs was lower than earlier suggested values. The space density for the subdwarf O stars is about 7x10^-7^pc^-3^, while the value for the subdwarf B stars is about 2x10^-6^pc^-3, both values considerably higher than previous estimates. The space densities can be used to place evolutionary constraints on these objects.
