IALP   13078
INSTITUTO DE ASTROFISICA LA PLATA
Unidad Ejecutora - UE
artículos
Título:
The impact of chemical differentiation of white dwarfs on thermonuclear supernovae
Autor/es:
BRAVO, EDUARDO; ALTHAUS, LEANDRO G.; GARCÍA-BERRO, ENRIQUE; DOMÍNGUEZ, INMACULADA
Revista:
ASTRONOMY AND ASTROPHYSICS
Editorial:
EDP SCIENCES S A
Referencias:
Año: 2011 vol. 526 p. 26 - 34
ISSN:
0004-6361
Resumen:
Aims: Gravitational settling of 22Ne in cooling white
dwarfs can affect the outcome of thermonuclear supernovae. We
investigate how the supernova energetics and nucleosynthesis are in turn
influenced by this process. We use realistic chemical profiles derived
from state-of-the-art white dwarf cooling sequences. The cooling
sequences provide a link between the white dwarf chemical structure and
the age of the supernova progenitor system. Methods: The cooling
sequence of a 1 Mȯ white dwarf was computed until
freezing using an up-to-date stellar evolutionary code. We computed
explosions of both Chandrasekhar mass and sub-Chandrasekhar mass white
dwarfs, assuming spherical symmetry and neglecting convective mixing
during the pre-supernova carbon simmering phase to maximize the effects
of chemical separation. Results: Neither gravitational settling
of 22Ne nor chemical differentiation of 12C and
16O have an appreciable impact on the properties of type Ia
supernovae, unless there is a direct dependence of the flame properties
(density of transition from deflagration to detonation) on the chemical
composition. At a fixed transition density, the maximum variation in the
supernova magnitude obtained from progenitors of different ages is ~0.06
mag, and even assuming an unrealistically large diffusion coefficient of
22Ne it would be less than ~0.09 mag. However, if the
transition density depends on the chemical composition (all other things
being equal) the oldest SNIa can be as much as 0.4 mag brighter than the
youngest ones (in our models the age difference is 7.4 Gyr). In
addition, our results show that 22Ne sedimentation cannot be
invoked to account for the formation of a central core of stable
neutron-rich Fe-group nuclei in the ejecta of sub-Chandrasekhar models,
as required by observations of type Ia supernovae.