Evolutionary and pulsational properties of white dwarf stars |
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Authors: | Leandro G Althaus Alejandro H Córsico Jordi Isern Enrique García-Berro |
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Institution: | (1) Space Research Institute, Russian Academy of Sciences, Profsoyuznaya Str. 84/32, 117997 Moskva, Russia;; |
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Abstract: | White dwarf stars are the final evolutionary stage of the vast majority of stars, including our Sun. Since the coolest white
dwarfs are very old objects, the present population of white dwarfs contains a wealth of information on the evolution of stars
from birth to death, and on the star formation rate throughout the history of our Galaxy. Thus, the study of white dwarfs
has potential applications in different fields of astrophysics. In particular, white dwarfs can be used as independent reliable
cosmic clocks, and can also provide valuable information about the fundamental parameters of a wide variety of stellar populations,
such as our Galaxy and open and globular clusters. In addition, the high densities and temperatures characterizing white dwarfs
allow these stars to be used as cosmic laboratories for studying physical processes under extreme conditions that cannot be
achieved in terrestrial laboratories. Last but not least, since many white dwarf stars undergo pulsational instabilities,
the study of their properties constitutes a powerful tool for applications beyond stellar astrophysics. In particular, white
dwarfs can be used to constrain fundamental properties of elementary particles such as axions and neutrinos and to study problems
related to the variation of fundamental constants. These potential applications of white dwarfs have led to renewed interest
in the calculation of very detailed evolutionary and pulsational models for these stars. In this work, we review the essentials
of the physics of white dwarf stars. We enumerate the reasons that make these stars excellent chronometers, and we describe
why white dwarfs provide tools for a wide variety of applications. Special emphasis is placed on the physical processes that
lead to the formation of white dwarfs as well as on the different energy sources and processes responsible for chemical abundance
changes that occur along their evolution. Moreover, in the course of their lives, white dwarfs cross different pulsational
instability strips. The existence of these instability strips provides astronomers with a unique opportunity to peer into
their internal structure that would otherwise remain hidden from observers. We will show that this allows one to measure stellar
masses with unprecedented precision and to infer their envelope thicknesses, to probe the core chemical stratification, and
to detect rotation rates and magnetic fields. Consequently, in this work, we also review the pulsational properties of white
dwarfs and the most recent applications of white dwarf asteroseismology. |
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