Mysterious Atmospheres of Cool White Dwarfs
Piotr Kowalski
German Research Centre for Geosciences Helmholtz Centre Potsdam, Germany
Cool white dwarfs are the remnants of the oldest stars that existed in
our Galaxy. Being billions of years old they can be used for dating old
stellar populations, the investigation of stars formation history and
derivation of internal composition of rocky exoplanets. The difficulties
in obtaining a reliable description of the physicochemical processes
prevailing in the extreme, fluid-like atmospheres of these stars limit
the full usage of white dwarfs for such purposes. In our work we study
the properties of condensed hydrogen and helium rich matter that
constitutes the atmospheres of these stars. The research is performed by
application of modern computational methods of materials science and
quantum chemistry. Our goal is to derive the reliable white dwarf
atmosphere models, which could be used for an in-depth analysis of the
rapidly growing data on cool white dwarfs. Such models will allow for
precise and definitive determination of the surface properties of these
stars. We will show the results of our recent studies of near-IR spectra
of cool, carbon-rich white dwarfs that independently support our recent
finding that the DQp stars are the DQ stars with pressure-shifted Swan
bands of C2. We will also show the UV spectra of selected cool
white dwarfs, indicating that the majority of the stars with Teff<5000 K
have hydrogen-rich atmospheres. Last but not least we will discuss
the remaining problems of the models in describing the near-IR and IR
spectra of very cool white dwarfs
Date: | Jeudi, le 28 juin 2012 |
Heure: | 11:30 |
Lieu: | Université de Montréal |
| Université de Montréal, Pavillon Roger-Gaudry, local D-460 |
Contact: | Pierre Bergeron |
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