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| Paper: |
Towards an Understanding of the Atmospheres of Cool White Dwarfs |
| Volume: |
469, 18th European White Dwarf Workshop (EUROWD12) |
| Page: |
173 |
| Authors: |
Kowalski, P. M.; Saumon, D.; Holberg, J.; Leggett, S. |
| Abstract: |
Cool white dwarfs with Teff < 6000 K are the remnants of the oldest stars that existed in our Galaxy.
Their atmospheres, when properly characterized, can provide valuable information on white dwarf evolution
and ultimately star formation through the history of the Milky Way. Understanding the atmospheres of these stars
requires joined observational effort and reliable atmosphere modeling.
We discuss and analyze recent observations of the near-ultraviolet (UV) and near-infrared (IR) spectrum of several cool white dwarfs
including DQ/DQp stars showing carbon in their spectra.
We present fits to the entire spectral energy distribution (SED) of selected cool stars,
showing that the current pure-hydrogen atmosphere models are quite reliable, especially in the near-UV spectral region.
Recently, we also performed an analysis
of the coolest known DQ/DQp stars investigating further the origin of the rm C2 Swan bands-like spectral features
that characterize the DQp stars. We show that the carbon abundances derived for DQp stars fit the trend of carbon abundance with Teff
seen in normal cool DQ stars. This further supports the recent conclusion of Kowalski (2010a) that
DQp stars are DQ stars with pressure distorted Swan bands.
However, we encounter some difficulties in reproducing the IR part of the SED of stars
having a mixed He/H atmosphere. This indicates limitations in current models of the opacity in dense He/H fluids. |
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