On the surface composition of cool, hydrogen-line white dwarfs - Discovery of helium in the atmospheres of cool DA stars and evidence for convective mixing

Bergeron, P.; Wesemaël, F.; Fontaine, G.; Liebert, James

doi:10.1086/185670

Cited by 67 publications

(58 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This problem was noted and discussed in Kleinman et al (2004) but has been known for decades and is likely a bias in the model atmospheres rather than the autofit algorithm. Bergeron et al (1990) first pointed out that the mean gravities and masses of DA white dwarfs cooler than the ZZ Ceti instability strip (<11,000 K ) are determined from pure hydrogen atmosphere models to be higher than for stars above this temperature. They suggested that the cool atmospheres could be moderately He-rich, as a result of incomplete convective mixing with the underlying He layer.…”

Section: Autofit Resultsmentioning

confidence: 99%

A Catalog of Spectroscopically Confirmed White Dwarfs from the Sloan Digital Sky Survey Data Release 4

Eisenstein¹,

Liebert²,

Harris³

et al. 2006

ASTROPHYS J SUPPL S

Self Cite

396

458

View full text Add to dashboard Cite

We present a catalog of 9316 spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey Data Release 4. We have selected the stars through photometric cuts and spectroscopic modeling, backed up by a set of visual inspections. About 6000 of the stars are new discoveries, roughly doubling the number of spectroscopically confirmed white dwarfs. We analyze the stars by performing temperature and surface gravity fits to grids of pure hydrogen and helium atmospheres. Among the rare outliers are a set of presumed helium-core DA white dwarfs with estimated masses below 0.3 M , including two candidates that may be the lowest-mass yet found. We also present a list of 928 hot subdwarfs.

show abstract

Section: Autofit Resultsmentioning

confidence: 99%

A Catalog of Spectroscopically Confirmed White Dwarfs from the Sloan Digital Sky Survey Data Release 4

Eisenstein¹,

Liebert²,

Harris³

et al. 2006

ASTROPHYS J SUPPL S

Self Cite

396

458

View full text Add to dashboard Cite

show abstract

“…Tremblay et al (2010, hereafter TB10; see also Koester et al 2009) made an extensive review of the possible solutions, which range from inadequate assumptions about the A&A 531, L19 (2011) composition of these stars to inaccuracies in the model atmosphere calculations. The non-detection of He i lines in highresolution Keck observations of cool DA stars by TB10 ruled out the systematic presence of helium in the atmospheres, which would mimic higher spectroscopic log g determinations, as initially proposed by Bergeron et al (1990). TB10 concluded -as Koester et al (2009) did -that a problem with the treatment of convective energy transport, currently based on the mixinglength theory (MLT;Böhm-Vitense 1958), is the only viable explanation for the high-log g problem.…”

Section: Introductionmentioning

confidence: 90%

Solution to the problem of the surface gravity distribution of cool DA white dwarfs from improved 3D model atmospheres

Tremblay

Ludwig

Steffen

et al. 2011

A&A

Self Cite

View full text Add to dashboard Cite

The surface gravities of cool (T eff < 13 000 K) hydrogen-atmosphere DA white dwarfs, determined from spectroscopic analyses, are found to be significantly higher than the canonical value of log g ∼ 8 expected for these stars. It was recently concluded that a problem with the treatment of convective energy transport within the framework of the mixing-length theory was the most plausible explanation for this high-log g problem. We pursue the investigation of this discrepancy by computing model spectra of cool convective white dwarfs from a small sequence (11 300 K < T eff < 12 800 K) of 3D hydrodynamical model atmospheres, which feature a sophisticated treatment of convection and radiative transfer. Our approach is to proceed with a differential analysis between 3D and standard 1D models. We find that the 3D spectra predict significantly lower surface gravities, with corrections of the right amplitude as a function of effective temperature to obtain values of log g ∼ 8 on average. We conclude that the surface gravity distribution of cool convective DA white dwarfs is much closer to that of hotter radiative objects when using, for the treatment of the convection, 3D models instead of the mixing-length framework.

show abstract

“…However, it can be used to demonstrate an effect well known for many years (Bergeron et al 1990a;Bergeron 1992;Kleinman et al 2004;Eisenstein et al 2006;Kepler et al 2007;DeGennaro et al 2008;Koester et al 2009). This is the fact that the surface gravity seems to increase around T eff ≈ 12 000 K towards lower temperatures.…”

Section: Continued Objectmentioning

confidence: 99%

High-resolution UVES/VLT spectra of white dwarfs observed for the ESO SN Ia Progenitor Survey

Koester¹,

Voß

Napiwotzki

et al. 2009

A&A

160

233

View full text Add to dashboard Cite

Context. The ESO Supernova Ia Progenitor Survey (SPY) took high-resolution spectra of more than 1000 white dwarfs and pre-white dwarfs. About two thirds of the stars observed are hydrogen-dominated DA white dwarfs. Here we present a catalog and detailed spectroscopic analysis of the DA stars in the SPY. Aims. Atmospheric parameters effective temperature and surface gravity are determined for normal DAs. Double-degenerate binaries, DAs with magnetic fields or dM companions, are classified and discussed. Methods. The spectra are compared with theoretical model atmospheres using a χ 2 fitting technique. Results. Our final sample contains 615 DAs, which show only hydrogen features in their spectra, although some are double-degenerate binaries. 187 are new detections or classifications. We also find 10 magnetic DAs (4 new) and 46 DA+dM pairs (10 new).

show abstract

On the surface composition of cool, hydrogen-line white dwarfs - Discovery of helium in the atmospheres of cool DA stars and evidence for convective mixing

Cited by 67 publications

References 0 publications

A Catalog of Spectroscopically Confirmed White Dwarfs from the Sloan Digital Sky Survey Data Release 4

A Catalog of Spectroscopically Confirmed White Dwarfs from the Sloan Digital Sky Survey Data Release 4

Solution to the problem of the surface gravity distribution of cool DA white dwarfs from improved 3D model atmospheres

High-resolution UVES/VLT spectra of white dwarfs observed for the ESO SN Ia Progenitor Survey

Contact Info

Product

Resources

About