- ID:
- ivo://CDS.VizieR/J/MNRAS/445/1331
- Title:
- White-dwarf + main-sequence binaries in SDSS DR9
- Short Name:
- J/MNRAS/445/1331
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 227 new spectroscopic white-dwarf + main-sequence (WDMS) binaries from the ninth data release (DR9) of the Sloan Digital Sky Survey (SDSS). The SDSS spectra of the newly found WDMS binaries with a DA white dwarf and an M-dwarf are analysed based on a spectral decomposition/fitting method. We obtain the effective temperatures, surface gravities and masses of the white dwarf, together with the spectral types and metallicities of the secondary star. Two independent distance estimates are derived from the flux-scaling factors between the WDMS SDSS spectra and the white dwarf and M-dwarf model spectra. We find that about 25 per cent of the newly found WDMS binaries show a significant discrepancy between the two distance estimates. This might be caused by the effects of M-dwarf stellar activity or irradiation of the M-dwarf companions by the white dwarf. The stellar parameter distributions are used to investigate the global properties of the newly found WDMS binaries. We find that the WDMS binaries with a low signal-to-noise ratio (S/N<=4.0) usually have a massive DA white dwarf component with a higher surface gravity, and the metallicity is usually significantly different from solar. This suggests that the observational selection effects and the spectral S/N of the WDMS binaries have a significant influence on the determinations of these physical parameters of WDMS binaries.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/484/5362
- Title:
- White dwarf+M dwarf binaries radial velocities
- Short Name:
- J/MNRAS/484/5362
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a radial velocity survey of 20 white dwarf plus M dwarf binaries selected as a follow up to a Hubble Space Telescope study that aimed to spatially resolve suspected binaries. Our candidates are taken from the list of targets that were spatially unresolved with Hubble. We have determined the orbital periods for 16 of these compact binary candidates. The period distribution ranges from 0.14 to 9.16d and peaks near 0.6d. The original sample therefore contains two sets of binaries, wide orbits (~100-1000au) and close orbits (~1-10au), with no systems found in the ~10-100au. This observational evidence confirms the bimodal distribution predicted by population models and is also similar to results obtained in previous studies. We find no binary periods in the months to years range, supporting the post common envelope evolution scenario. One of our targets, WD 1504+546, was discovered to be an eclipsing binary with a period of 0.93d.
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/2102
- Title:
- White dwarf population from the SDSS DR12
- Short Name:
- J/MNRAS/469/2102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Sloan Digital Sky Survey Data Release 12, which is the largest available white dwarf catalogue to date, to study the evolution of the kinematical properties of the population of white dwarfs in the Galactic disc. We derive masses, ages, photometric distances and radial velocities for all white dwarfs with hydrogen-rich atmospheres. For those stars for which proper motions from the USNO-B1 catalogue are available, the true three-dimensional components of the stellar space velocity are obtained. This subset of the original sample comprises 20 247 objects, making it the largest sample of white dwarfs with measured three-dimensional velocities. Furthermore, the volume probed by our sample is large, allowing us to obtain relevant kinematical information. In particular, our sample extends from a Galactocentric radial distance R_G_=7.8 to 9.3kpc, and vertical distances from the Galactic plane ranging from Z=-0.5 to 0.5kpc. We examine the mean components of the stellar three-dimensional velocities, as well as their dispersions with respect to the Galactocentric and vertical distances. We confirm the existence of a mean Galactocentric radial velocity gradient, {partial}<V_R_>/{partial}R_G_=-3+/-5km/s/. We also confirm north-south differences in <V_z_> . Specifically, we find that white dwarfs with Z>0 (in the North Galactic hemisphere) have <V_z_><0, while the reverse is true for white dwarfs with Z<0. The age-velocity dispersion relation derived from the present sample indicates that the Galactic population of white dwarfs may have experienced an additional source of heating, which adds to the secular evolution of the Galactic disc.
- ID:
- ivo://CDS.VizieR/J/ApJ/867/62
- Title:
- White dwarf population of Messier 67
- Short Name:
- J/ApJ/867/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarfs (WDs) are excellent forensic tools for studying end-of-life issues surrounding low- and intermediate-mass stars, and the old, solar metallicity open star cluster Messier 67 is a proven laboratory for the study of stellar evolution for solar-type stars. In this paper, we present a detailed spectroscopic study of brighter (M_g_<=12.4) WDs in Messier 67, and in combination with previously published proper motion membership determinations, we identify a clean, representative sample of cluster WDs, including 13 members with hydrogen-dominated atmospheres, at least one of which is a candidate double degenerate, and 5 members with helium-dominated atmospheres. Using this sample we test multiple predictions surrounding the final stages of stellar evolution in solar-type stars. In particular, the stochasticity of the integrated mass lost by ~1.5 solar mass stars is less than 7% of the WD remnant mass. We identify WDs likely resulting from binary evolution, including at least one blue straggler remnant and two helium-core WDs. We observe no evidence of a significant population of helium-core WDs formed by enhanced mass loss on the red giant branch of the cluster. The distribution of WD atmospheric compositions is fully consistent with that in the field, limiting proposed mechanisms for the suppression of helium atmosphere WD formation in star clusters. In short, the WD population of Messier 67 is fully consistent with basic predictions of single- and multiple-star stellar evolution theories for solar metallicity stars.
- ID:
- ivo://CDS.VizieR/J/A+A/486/843
- Title:
- White dwarf-red dwarf binaries in the SDSS
- Short Name:
- J/A+A/486/843
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To reduce contamination by more distant sources, such as quasars, we have selected candidate white dwarf-red dwarf binaries from the catalogue of proper motion stars drawn from the intersection of the Sloan Digital Sky Survey (SDSS) and the USNO-B1.0 catalogue.
- ID:
- ivo://CDS.VizieR/J/A+A/400/877
- Title:
- White dwarfs 3D kinematics from SPY project
- Short Name:
- J/A+A/400/877
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present kinematics of a sample of 107 DA white dwarfs from the SPY project (ESO SN Ia Progenitor surveY) and discuss kinematic criteria for a distinction of thin disk, thick disk, and halo populations. This is the first homogeneous sample of white dwarfs for which 3D space motions have been determined. Since the percentage of old stars among white dwarfs is higher than among main-sequence stars, they are presumably valuable tools in studies of old populations such as the halo and the thick disk. Studies of white dwarf kinematics can help to determine the fraction of the total mass of our Galaxy contained in the form of thick disk and halo white dwarfs, an issue which is still under discussion. Radial velocities and spectroscopic distances obtained by the SPY project are combined with our measurements of proper motions to derive 3D space motions. Galactic orbits and further kinematic parameters are computed. We calculate individual errors of kinematic parameters by means of a Monte Carlo error propagation code. Our kinematic criteria for assigning population membership are deduced from a sample of F and G stars taken from the literature for which chemical criteria can be used to distinguish between thin disk, thick disk and halo. Candidates for thick disk and halo members are selected in a first step from the classical U-V-velocity diagram. Our final assignment of population membership is based on orbits and position in the J_z_-eccentricity diagram. We find four halo and twelve thick disk white dwarfs. We also present a systematic study of the effects of ignoring the radial velocity in kinematic investigations.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/1037
- Title:
- White dwarfs from the Kiso survey
- Short Name:
- J/ApJ/714/1037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic analysis of white dwarfs found in the Kiso survey. Spectroscopic observations at high signal-to-noise ratio have been obtained for all DA and DB stars in the Kiso Schmidt ultraviolet excess survey (KUV stars). These observations led to the reclassification of several KUV objects, including the discovery of three unresolved DA+DB double-degenerate binaries. The atmospheric parameters (T_eff_ and logg) are obtained from detailed model atmosphere fits to optical spectroscopic data. The mass distribution of our sample is characterized by a mean value of 0.606M_{sun}_ and a dispersion of 0.135M_{sun}_ for DA stars, and 0.758M_{sun}_ and a dispersion of 0.192M_{sun}_ for DB stars. Absolute visual magnitudes obtained from our spectroscopic fits allow us to derive an improved luminosity function for the DA and DB stars identified in the Kiso survey. Our luminosity function is found to be significantly different from earlier estimates based on empirical photometric calibrations of M_V_ for the same sample. The results for the DA stars now appear entirely consistent with those obtained for the PG survey using the same spectroscopic approach. The space density for DA stars with M_V_<=12.75 is 2.80x10^-4^pc^-3^ in the Kiso survey, which is 9.6% smaller than the value found in the PG survey.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/1988
- Title:
- White dwarfs in Galactic plane
- Short Name:
- J/MNRAS/457/1988
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated the prospects for systematic searches of white dwarfs at low Galactic latitudes, using the VLT Survey Telescope H{alpha} Photometric Survey of the Galactic plane and Bulge (VPHAS+). We targeted 17 white dwarf candidates along sightlines of known open clusters, aiming to identify potential cluster members. We confirmed all the 17 white dwarf candidates from blue/optical spectroscopy, and we suggest five of them to be likely cluster members. We estimated progenitor ages and masses for the candidate cluster members, and compare our findings to those for other cluster white dwarfs. A white dwarf in NGC 3532 is the most massive known cluster member (1.13M_{sun}_), likely with an oxygen-neon core, for which we estimate an M_{sun}_ progenitor, close to the mass-divide between white dwarf and neutron star progenitors. A cluster member in Ruprecht 131 is a magnetic white dwarf, whose progenitor mass exceeded 2-3M_{sun}_. We stress that wider searches, and improved cluster distances and ages derived from data of the ESA Gaia mission, will advance the understanding of the mass-loss processes for low- to intermediate-mass stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/3241
- Title:
- White dwarfs in SDSS Stripe 82
- Short Name:
- J/MNRAS/473/3241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Binary evolution theory predicts that accreting white dwarfs with substellar companions dominate the Galactic population of cataclysmic variables (CVs). In order to test these predictions, it is necessary to identify these systems, which may be difficult if the signatures of accretion become too weak to be detected. The only chance to identify such 'dead' CVs is by exploiting their close binary nature. We have therefore searched the Sloan Digital Sky Survey (SDSS) Stripe 82 area for apparently isolated white dwarfs that undergo eclipses by a dark companion. We found no such eclipses in either the SDSS or Palomar Transient Factory data sets among our sample of 2264 photometrically selected white dwarf candidates within Stripe 82. This null result allows us to set a firm upper limit on the space density, {rho}0, of dead CVs. In order to determine this limit, we have used Monte Carlo simulations to fold our selection criteria through a simple model of the Galactic CV distribution. Assuming a T_WD_=7500K, the resulting 2{sigma} limit on the space density of dead CVs is {rho}0<~2x10^-5^pc^-3^, where TWD is the typical effective temperature of the white dwarf in such systems.
21390. White Dwarfs in the SDSS
- ID:
- ivo://CDS.VizieR/J/AJ/126/1023
- Title:
- White Dwarfs in the SDSS
- Short Name:
- J/AJ/126/1023
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An initial assessment is made of white dwarf and hot subdwarf stars observed in the Sloan Digital Sky Survey. In a small area of sky (190 square degrees), observed much like the full survey will be, 269 white dwarfs (WDs) and 56 hot subdwarfs are identified spectroscopically where only 44 white dwarfs and five hot subdwarfs were known previously. Most are ordinary DA (hydrogen atmosphere) and DB (helium) types. In addition, in the full survey to date, a number of WDs have been found with uncommon spectral types. Among these are blue DQ stars displaying lines of atomic carbon; red DQ stars showing molecular bands of C2 with a wide variety of strengths; DZ stars where Ca and occasionally Mg, Na, and/or Fe lines are detected; and magnetic WDs with a wide range of magnetic field strengths in DA, DB, DQ, and (probably) DZ spectral types. Photometry alone allows identification of stars hotter than 12000K, and the density of these stars for magnitude g 15<g<20 is found to be ~2.2deg^-2^ at Galactic latitudes of 29{deg}-62{deg}. Spectra are obtained for roughly half of these hot stars. The spectra show that for 15<g<17, 40% of hot stars are WDs, and the fraction of WDs rises to ~90% at g=20. The remainder are hot sdB and sdO stars.
