Alejandro H. Córsico, Alejandra D. Romero, Leandro G. Althaus, Marcelo M. Miller Bertolami
Asteroseismology of DAV stars (ZZ Ceti variables) can provide valuable clues
about the origin, structure and evolution of DA (atmospheres rich in H) white
dwarfs. Recently, a new DAV star, WD J191643.83+393849.7, has been discovered
in the field of the Kepler spacecraft. It is expected that further monitoring
of this star in the next years will enable astronomers to obtain the best
lightcurve of a pulsating DA white dwarf ever recorded, and thus to know with
unprecedented precision the hidden details of the internal structure of this
star. In this paper, we perform a first asteroseismological analysis of WD
J191643.83+393849.7 on the basis of fully evolutionary DA white-dwarf models.
Specifically, we employ a complete set of evolutionary DA white-dwarf
structures covering a wide range of effective temperatures, stellar masses, and
H envelope thicknesses. These models have been obtained on the basis of a
complete treatment of the evolutionary history of progenitors stars. We compute
g-mode adiabatic pulsation periods for this set of models and compare them with
the pulsation periods exhibited by WD J191643.83+393849.7. Based on a tentative
estimation of the mean period spacing of the star, we find that the stellar
mass should be substantially large ($\gtrsim 0.80 M_{\odot}$), in agreement
with the spectroscopically derived stellar mass. Also, from period-to-period
fits we find an asteroseismological model characterised by a low effective
temperature, rather high stellar mass and a thin H envelope. The possibility
that this rather massive pulsating white dwarf can be further monitored with
Kepler with a high degree of detail turns the star WD J191643.83+393849.7 into
a promising and unique object to study the physics of crystallization and
carbon/oxygen phase diagrams at high densities.
View original:
http://arxiv.org/abs/1112.4805
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