IALP   13078
INSTITUTO DE ASTROFISICA LA PLATA
Unidad Ejecutora - UE
artículos
Título:
Quiescent Nuclear Burning in Low-metallicity White Dwarfs
Autor/es:
M. M. MILLER BERTOLAMI; L. G. ALTHAUS; GARCIA-BERRO, E.
Revista:
Astrophysical Journal Letters
Editorial:
IOP Publishing
Referencias:
Lugar: Philadelphia; Año: 2013 vol. 775 p. 22 - 26
ISSN:
2041-8205
Resumen:
We discuss the impact of residual nuclear burning in the cooling
sequences of hydrogen-rich (DA) white dwarfs with very low metallicity
progenitors (Z = 0.0001). These cooling sequences are appropriate for
the study of very old stellar populations. The results presented here
are the product of self-consistent, fully evolutionary calculations.
Specifically, we follow the evolution of white dwarf progenitors from
the zero-age main sequence through all the evolutionary phases, namely
the core hydrogen-burning phase, the helium-burning phase, and the
thermally pulsing asymptotic giant branch phase to the white dwarf
stage. This is done for the most relevant range of main-sequence masses,
covering the most usual interval of white dwarf masses?from 0.53 M
⊙ to 0.83 M ⊙. Due to the low metallicity
of the progenitor stars, white dwarfs are born with thicker hydrogen
envelopes, leading to more intense hydrogen burning shells as compared
with their solar metallicity counterparts. We study the phase in which
nuclear reactions are still important and find that nuclear energy
sources play a key role during long periods of time, considerably
increasing the cooling times from those predicted by standard white
dwarf models. In particular, we find that for this metallicity and for
white dwarf masses smaller than about 0.6 M ⊙, nuclear
reactions are the main contributor to the stellar luminosity for
luminosities as low as log (L/L ⊙) ~= -3.2. This,
in turn, should have a noticeable impact in the white dwarf luminosity
function of low-metallicity stellar populations.