Equilibrium structure of white dwarfs at finite temperatures

Recently, it has been shown by S. M. de Carvalho et al. (2014) that the deviations between the degenerate case and observations were already evident for 0.7-0.8 M[Formula: see text] white dwarfs. Such deviations were related to the neglected effects of finite temperatures on the structure of a white dwarf. Therefore, in this work by employing the Chandrasekhar equation of state taking into account the effects of temperature we show how the total pressure of the white dwarf matter depends on the mass density at different temperatures. Afterwards we construct equilibrium configurations of white dwarfs at finite temperatures. We obtain the mass-radius relations of white dwarfs for different temperatures by solving the Tolman-Oppenheimer-Volkoff equation, and compare them with the estimated masses and radii inferred from the Sloan Digital Sky Survey Data Release 4.

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White Dwarf Stars

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194517600230 ◽

2017 ◽

Vol 45 ◽

pp. 1760023

Author(s):

S. O. Kepler ◽

Alejandra Daniela Romero ◽

Ingrid Pelisoli ◽

Gustavo Ourique

Keyword(s):

White Dwarf ◽

Final Stage ◽

White Dwarfs ◽

Sloan Digital Sky Survey ◽

Dwarf Stars ◽

Multiple Systems ◽

White Dwarf Stars ◽

Sky Survey ◽

Data Release ◽

Low Mass

White dwarf stars are the final stage of most stars, born single or in multiple systems. We discuss the identification, magnetic fields, and mass distribution for white dwarfs detected from spectra obtained by the Sloan Digital Sky Survey up to Data Release 13 in 2016, which lead to the increase in the number of spectroscopically identified white dwarf stars from 5[Formula: see text]000 to 39[Formula: see text]000. This number includes only white dwarf stars with [Formula: see text], i.e., excluding the Extremely Low Mass white dwarfs, which are necessarily the byproduct of stellar interaction.

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The frequency of gaseous debris discs around white dwarfs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa359 ◽

2020 ◽

Vol 493 (2) ◽

pp. 2127-2139 ◽

Cited By ~ 13

Author(s):

Christopher J Manser ◽

Boris T Gänsicke ◽

Nicola Pietro Gentile Fusillo ◽

Richard Ashley ◽

Elmé Breedt ◽

...

Keyword(s):

White Dwarf ◽

White Dwarfs ◽

Signal To Noise Ratio ◽

Infrared Emission ◽

Sloan Digital Sky Survey ◽

Emission Lines ◽

Occurrence Rate ◽

Limited Sample ◽

Sky Survey ◽

Gaseous Disc

ABSTRACT A total of 1–3 per cent of white dwarfs are orbited by planetary dusty debris detectable as infrared emission in excess above the white dwarf flux. In a rare subset of these systems, a gaseous disc component is also detected via emission lines of the Ca ii 8600 Å triplet, broadened by the Keplerian velocity of the disc. We present the first statistical study of the fraction of debris discs containing detectable amounts of gas in emission at white dwarfs within a magnitude and signal-to-noise ratio limited sample. We select 7705 single white dwarfs spectroscopically observed by the Sloan Digital Sky Survey (SDSS) and Gaia with magnitudes g ≤ 19. We identify five gaseous disc hosts, all of which have been previously discovered. We calculate the occurrence rate of a white dwarf hosting a debris disc detectable via Ca ii emission lines as $0.067\, \pm \, ^{0.042}_{0.025}$ per cent. This corresponds to an occurrence rate for a dusty debris disc to have an observable gaseous component in emission as 4 ± $_{2}^{4}$ per cent. Given that variability is a common feature of the emission profiles of gaseous debris discs, and the recent detection of a planetesimal orbiting within the disc of SDSS J122859.93+104032.9, we propose that gaseous components are tracers for the presence of planetesimals embedded in the discs and outline a qualitative model. We also present spectroscopy of the Ca ii triplet 8600 Å region for 20 white dwarfs hosting dusty debris discs in an attempt to identify gaseous emission. We do not detect any gaseous components in these 20 systems, consistent with the occurrence rate that we calculated.

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Pulsating white dwarfs in cataclysmic variables: The marriage of ZZ Cet and dwarf nova

International Astronomical Union Colloquium ◽

10.1017/s0252921100010988 ◽

2004 ◽

Vol 193 ◽

pp. 382-386 ◽

Cited By ~ 3

Author(s):

Brian Warner ◽

Patrick A. Woudt

Keyword(s):

White Dwarf ◽

Large Amplitude ◽

White Dwarfs ◽

Cataclysmic Variables ◽

Sloan Digital Sky Survey ◽

Dwarf Novae ◽

Dwarf Nova ◽

Sky Survey

AbstractThere are now four dwarf novae known with white dwarf primaries that show large amplitude non-radial oscillations of the kind seen in ZZ Cet stars. We compare the properties of these stars and point out that by the end of the Sloan Digital Sky Survey more than 30 should be known.

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White dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 14

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz960 ◽

2019 ◽

Vol 486 (2) ◽

pp. 2169-2183 ◽

Cited By ~ 24

Author(s):

S O Kepler ◽

Ingrid Pelisoli ◽

Detlev Koester ◽

Nicole Reindl ◽

Stephan Geier ◽

...

Keyword(s):

Survey Data ◽

White Dwarf ◽

White Dwarfs ◽

Main Sequence ◽

Sloan Digital Sky Survey ◽

Dwarf Stars ◽

White Dwarf Stars ◽

Sky Survey ◽

Data Release ◽

Hot Subdwarfs

ABSTRACT White dwarfs carry information on the structure and evolution of the Galaxy, especially through their luminosity function and initial-to-final mass relation. Very cool white dwarfs provide insight into the early ages of each population. Examining the spectra of all stars with 3σ proper motion in the Sloan Digital Sky Survey Data Release 14, we report the classification for 20 088 spectroscopically confirmed white dwarfs, plus 415 hot subdwarfs, and 311 cataclysmic variables. We obtain Teff, log g, and mass for hydrogen atmosphere white dwarf stars (DAs), warm helium atmosphere white dwarfs (DBs), hot subdwarfs (sdBs and sdOs), and estimate photometric Teff for white dwarf stars with continuum spectra (DCs). We find 15 793 sdAs and 447 dCs between the white dwarf cooling sequence and the main sequence, especially below $T_\mathrm{eff}\simeq 10\, 000$ K; most are likely low-mass metal-poor main-sequence stars, but some could be the result of interacting binary evolution.

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Computational tools for the spectroscopic analysis of white dwarfs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2165 ◽

2020 ◽

Vol 497 (3) ◽

pp. 2688-2698 ◽

Cited By ~ 2

Author(s):

Vedant Chandra ◽

Hsiang-Chih Hwang ◽

Nadia L Zakamska ◽

Tamás Budavári

Keyword(s):

White Dwarf ◽

White Dwarfs ◽

Spectroscopic Analysis ◽

Theoretical Models ◽

Sloan Digital Sky Survey ◽

Random Forest Regression ◽

Computational Tools ◽

Sky Survey ◽

Stellar Photosphere ◽

Temperature Surface

ABSTRACT The spectroscopic features of white dwarfs are formed in the thin upper layer of their stellar photosphere. These features carry information about the white dwarf’s surface temperature, surface gravity, and chemical composition (hereafter ‘labels’). Existing methods to determine these labels rely on complex ab-initio theoretical models, which are not always publicly available. Here, we present two techniques to determine atmospheric labels from white dwarf spectra: a generative fitting pipeline that interpolates theoretical spectra with artificial neural networks and a random forest regression model using parameters derived from absorption line features. We test and compare our methods using a large catalogue of white dwarfs from the Sloan Digital Sky Survey (SDSS), achieving the same accuracy and negligible bias as compared to previous studies. We package our techniques into an open-source python module ‘wdtools’ that provides a computationally inexpensive way to determine stellar labels from white dwarf spectra observed from any facility. We will actively develop and update our tool as more theoretical models become publicly available. We discuss applications of our tool in its present form to identify interesting outlier white dwarf systems including those with magnetic fields, helium-rich atmospheres, and double-degenerate binaries.

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A catalogue of white dwarfs in Gaia EDR3

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab2672 ◽

2021 ◽

Author(s):

N P Gentile Fusillo ◽

P-E Tremblay ◽

E Cukanovaite ◽

A Vorontseva ◽

R Lallement ◽

...

Keyword(s):

Effective Temperature ◽

White Dwarf ◽

Proper Motion ◽

White Dwarfs ◽

Absolute Magnitude ◽

Sloan Digital Sky Survey ◽

Atmospheric Models ◽

Sky Survey ◽

Cross Match ◽

Temperature Surface

Abstract We present a catalogue of white dwarf candidates selected from Gaia early data release three (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 30 000 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 DR2 to calculate a probability of being a white dwarf (PWD) for ≃ 1.3 million sources which passed our quality selection. The PWD values can be used to select a sample of ≃ 359 000 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 ≤ 20 mag and effective temperature (Teff) >7000 K, at high Galactic latitudes (|b| > 20○). Alongside the main catalogue we include a reduced-proper-motion extension containing ≃ 10 200 white dwarf candidates with unreliable parallax measurements which could, however be identified on the basis of their proper motion. We also performed a cross-match of our catalogues with SDSS DR16 spectroscopy and provide spectral classification based on visual inspection for all resulting matches.

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WHITE DWARF LUMINOSITY AND MASS FUNCTIONS FROM SLOAN DIGITAL SKY SURVEY SPECTRA

The Astronomical Journal ◽

10.1088/0004-6256/135/1/1 ◽

2007 ◽

Vol 135 (1) ◽

pp. 1-9 ◽

Cited By ~ 56

Author(s):

Steven DeGennaro ◽

Ted von Hippel ◽

D. E. Winget ◽

S. O. Kepler ◽

Atsuko Nitta ◽

...

Keyword(s):

White Dwarf ◽

Sloan Digital Sky Survey ◽

Sky Survey ◽

Mass Functions

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New DQ white dwarfs in the Sloan Digital Sky Survey DR4: confirmation of two sequences

Astronomy and Astrophysics ◽

10.1051/0004-6361:20065287 ◽

2006 ◽

Vol 454 (3) ◽

pp. 951-956 ◽

Cited By ~ 37

Author(s):

D. Koester ◽

S. Knist

Keyword(s):

White Dwarfs ◽

Sloan Digital Sky Survey ◽

Sky Survey

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AM Herculis Binaries

Symposium - International Astronomical Union ◽

10.1017/s0074180900055868 ◽

1996 ◽

Vol 165 ◽

pp. 403-414 ◽

Cited By ~ 2

Author(s):

K. Beuermann

Keyword(s):

White Dwarf ◽

White Dwarfs ◽

Close Binaries ◽

Physical Processes ◽

X Ray ◽

Sky Survey

AM Herculis binaries contain mass accreting magnetic white dwarfs which appear as bright X-ray sources in the ROSAT All Sky Survey. About 52 systems are presently known which allow detailed studies of the evolution of magnetic close binaries and of fundamental plasma-physical processes in the accretion region on the white dwarf.

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