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The spectral evolution of hot white dwarfs

Published online by Cambridge University Press:  09 October 2020

Antoine Bédard Open the ORCID record for Antoine Bédard [Opens in a new window] ,
Pierre Bergeron  and
Gilles Fontaine
Antoine Bédard
Affiliation:
Département de Physique, Université de Montréal, Montréal, QC H3C 3J7, Canada emails: [email protected], [email protected]
Pierre Bergeron
Affiliation:
Département de Physique, Université de Montréal, Montréal, QC H3C 3J7, Canada emails: [email protected], [email protected]
Gilles Fontaine
Affiliation:
Département de Physique, Université de Montréal, Montréal, QC H3C 3J7, Canada emails: [email protected], [email protected]
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Abstract

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As they evolve, white dwarfs undergo major changes in their atmospheric composition, a phenomenon known as spectral evolution. In particular, most hot He-rich (DO) stars transform into H-rich (DA) stars as they cool off, most likely as a result of the float-up of residual H. We investigate this DO-to-DA transition by taking advantage of the extensive spectroscopic dataset provided by the Sloan Digital Sky Survey (SDSS). Using our new state-of-the-art non-LTE model atmospheres, we perform a spectroscopic analysis of 1882 hot (Teff >30,000 K) white dwarfs identified in the SDSS. We find that at least 15% of all white dwarfs are born with a He-dominated atmosphere. Among these, ∼2/3 turn into H-rich stars before they reach Teff ∼40,000 K, while the remaining ∼1/3 maintain their He-rich surface throughout their entire evolution. We speculate on the origin of these two groups of objects.

Keywords

diffusionstars: abundancesstars: atmospheresstars: evolutionwhite dwarfs
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 15 , Symposium S357: White Dwarfs as Probes of Fundamental Physics: Tracers of Planetary, Stellar and Galactic Evolution , October 2019 , pp. 162 - 165
Copyright
© International Astronomical Union 2020

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