Toward High Precision Seismic Studies of White Dwarf Stars: Parametrization of the Core and Tests of Accuracy

Abstract

We present a prescription for parametrizing the chemical profile in the core of white dwarfs in the light of the recent discovery that pulsation modes may sometimes be deeply confined in some cool pulsating white dwarfs. Such modes may be used as unique probes of the complicated chemical stratification that results from several processes that occurred in previous evolutionary phases of intermediate-mass stars. This effort is part of our ongoing quest for more credible and realistic seismic models of white dwarfs using static, parametrized equilibrium structures. Inspired from successful techniques developed in design optimization fields (such as aerodynamics), we exploit Akima splines for the tracing of the chemical profile of oxygen (carbon) in the core of a white dwarf model. A series of tests are then presented to better seize the precision and significance of the results that can be obtained in an asteroseismological context. We also show that the new parametrization passes an essential basic test, as it successfully reproduces the chemical stratification of a full evolutionary model.

arXiv comment70 pages, 18 figures, 17 tables, accepted for publication in the Astrophysical Journal Supplement

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• The potential of asteroseismology for probing the core chemical stratification in white dwarf stars
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• Pulsating White Dwarfs
• New DA white dwarf models for asteroseismology of ZZ Ceti stars
• Properties and Asteroseismological analysis of a new ZZ ceti discovered by TMTS
• Asteroseismology of the pulsating extremely low-mass white dwarf SDSS J111215.82+111745.0: a model with $p$-mode pulsations consistent with the observations