J/ApJ/901/93 Model atmosphere analysis of hot WDs from SDSS DR12 (Bedard+, 2020)
On the spectral evolution of hot white dwarf stars.
I. A detailed model atmosphere analysis of hot white dwarfs from SDSS DR12.
Bedard A., Bergeron P., Brassard P., Fontaine G.
<Astrophys. J., 901, 93 (2020)>
=2020ApJ...901...93B 2020ApJ...901...93B
ADC_Keywords: Stars, white dwarf; Spectra, optical; Spectral types;
Stars, masses; Stars, diameters; Effective temperatures
Keywords: White dwarf stars ; Late stellar evolution ; Atmospheric
composition ; Stellar atmospheres
Abstract:
As they evolve, white dwarfs undergo major changes in surface
composition, a phenomenon known as spectral evolution. In particular,
some stars enter the cooling sequence with helium atmospheres
(type DO) but eventually develop hydrogen atmospheres (type DA), most
likely through the upward diffusion of residual hydrogen. Our
empirical knowledge of this process remains scarce: the fractions of
white dwarfs that are born helium rich and that experience the
DO-to-DA transformation are poorly constrained. We tackle this issue
by performing a detailed model-atmosphere investigation of 1806 hot
(Teff≥30000K) white dwarfs observed spectroscopically by the Sloan
Digital Sky Survey. We first introduce our new generations of model
atmospheres and theoretical cooling tracks, both appropriate for hot
white dwarfs. We then present our spectroscopic analysis, from which
we determine the atmospheric and stellar parameters of our sample
objects. We find that ∼24% of white dwarfs begin their degenerate life
as DO stars, among which ∼2/3 later become DA stars. We also infer
that the DO-to-DA transition occurs at substantially different
temperatures (75000K>Teff>30000K) for different objects, implying a
broad range of hydrogen content within the DO population. Furthermore,
we identify 127 hybrid white dwarfs, including 31 showing evidence of
chemical stratification, and we discuss how these stars fit in our
understanding of the spectral evolution. Finally, we uncover
significant problems in the spectroscopic mass scale of very hot
(Teff>60000K) white dwarfs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 125 1806 Atmospheric and stellar parameters of hot
white dwarfs from SDSS DR12
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See also:
II/207 : Palomar-Green catalog UV-excess stellar objects (Green+ 1986)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
J/ApJS/133/413 : BVRIJHK photometry of cool white dwarfs (Bergeron+, 2001)
J/ApJS/156/47 : DA WDs from the Palomar Green Survey (Liebert+, 2005)
J/ApJS/167/40 : SDSS4 confirmed white dwarfs catalog (Eisenstein+, 2006)
J/AJ/132/676 : SDSS hot DB white dwarfs (Eisenstein+, 2006)
J/ApJ/652/1554 : Iron in hot DA white dwarfs (Vennes+, 2006)
J/ApJ/743/138 : Spectroscopic survey of bright WDs (Gianninas+, 2011)
J/ApJ/730/128 : Spectroscopy of DA WD from the SDSS-DR4 (Tremblay+, 2011)
J/ApJS/204/5 : SDSS DR7 white dwarf catalog (Kleinman+, 2013)
J/A+A/555/A96 : White dwarf cooling timescales (Salaris+, 2013)
J/A+A/583/A86 : DB white dwarfs in SDSS DR10 and DR12 (Koester+, 2015)
J/MNRAS/446/4078 : New white dwarf stars in SDSS DR10 (Kepler+, 2015)
J/MNRAS/455/3413 : New WD and subdwarf stars in SDSS DR12 (Kepler+, 2016)
J/ApJ/848/11 : Spectroscopic & photometric analysis of WDs (Bedard+, 2017)
J/MNRAS/480/1547 : Full Evolutionary Sequences of Massive WDs (Lauffer+, 2018)
J/ApJ/878/63 : Cool WD atmosphere models. IV. (Blouin+, 2019)
J/ApJ/885/74 : 1340 Helium rich white dwarfs in the Gaia era (Coutu+, 2019)
J/ApJ/882/106 : DB WDs with SDSS and Gaia data (Genest-Beaulieu+, 2019)
J/A+A/628/A102 : Carbon-rich (DQ) white dwarfs in SDSS (Koester+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS SDSS identifier (JHHMMSS.ss+DDMMSS.s)
21- 25 A5 --- SpT Spectral type
27- 31 F5.1 --- S/N [2.2/132.5] Signal-to-Noise
33- 38 I6 K Teff [30000/150000] Effective temperature
40- 44 I5 K e_Teff [53/44228] Uncertainty in Teff
46- 49 F4.2 [cm/s2] log(g) [6.42/9.36] log surface gravity
51- 54 F4.2 [cm/s2] e_log(g) [0.01/1.33] Uncertainty in log(g)
56- 72 A17 --- Atm Atmospheric composition
74- 77 F4.2 Msun Mass [0.23/1.32] Mass
79- 82 F4.2 Msun e_Mass [0.01/0.52] Uncertainty in Mass
84- 89 F6.4 Rsun Rad [0.004/0.072] Radius
91- 96 F6.4 Rsun e_Rad [0.0001/0.03] Uncertainty in Rad
98-102 F5.2 [Lsun] logL [-1.88/3.15] log Luminosity
104-107 F4.2 [Lsun] e_logL [0.01/1.4] Uncertainty in logL
109 A1 --- l_logtau Limit flag on logtau
111-114 F4.2 [yr] logtau [5.0/8.48] log cooling age
116-119 F4.2 [yr] e_logtau [0.01/1.8]? Uncertainty in logtau
121-125 A5 --- Note Note codes (1)
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Note (1): Code as follows:
1 = The contribution of the main-sequence companion to the spectrum
was removed before performing the fit.
2 = At least one line core is filled with emission and was excluded
from the fit.
3 = The given parameters were obtained from chemically stratified model
atmospheres, which yield a better fit to the hybrid spectrum.
4 = The given parameters were obtained from chemically homogeneous model
atmospheres, which yield a better fit to the hybrid spectrum.
5 = The spectrum exhibits the Balmer-line problem and was fitted with the
CNO-rich model atmospheres of Gianninas+ 2010ApJ...720..581G 2010ApJ...720..581G
6 = The traces of carbon were neglected in the model-atmosphere
calculations, and the weak C IV lines were excluded from the fit.
7 = At least one line was excluded from the fit due to the presence of a
glitch or to an incomplete wavelength coverage.
8 = The main He II lines are abnormally strong and were excluded from
the fit.
9 = The given parameters are meaningless since the hybrid spectrum is
actually produced by a DA+DO/DB binary system.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Jan-2022