IALP   13078
INSTITUTO DE ASTROFISICA LA PLATA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Evolution of hydrogen-deficient white dwarfs
Autor/es:
ROHRMANN, R. D. ; ALTHAUS, L. G.; CÓRSICO, A. H.; CAMISASSA, M. E.; GARCÍA BERRO, E.
Lugar:
Coventry
Reunión:
Workshop; 20th European White Dwarf Workshop; 2016
Institución organizadora:
The Univestity of Warwick
Resumen:
We present full evolutionary calculations appropriate for the study of hydrogen-deficient DB white dwarfs. This is done by evolving white dwarf progenitors from the zero-age main sequence, through the core hydrogen-burning phase, the helium-burning phase, and the thermally pulsing asymptotic giant branch phase to the white dwarf stage. These models experienced a late thermal pulse during the asymptotic giant branch phase and, consequently, most of their hydrogen content is burned. As a result, our white dwarfs models are born with hydrogen-deficient atmospheres. Complete evolutionary sequences are computed for a metallicity representative of the solar neighborhood (Z=0.02), considering a wide range of stellar masses. During the white dwarf cooling stage, we self-consistently compute the phase in which nuclear reactions are still important, the diffusive evolution of the elements in the outer layers and, finally, we also take into account all the relevant energy sources in the deep interior of the white dwarf, such as the release of latent heat and the release of gravitational energy due to carbon-oxygen phase separation upon crystallization. As well known, the treatment of the outer boundary conditions is a key aspect concerning the evolutionary properties of cool hydrogen-deficient white dwarfs, hence for the cooling sequences presented here, outer boundary conditions are based on a new set of improved non-gray white dwarf model atmospheres for pure helium composition (Rohrmann 2016), which include the most up-to-date physical inputs. The calculations are extended down to an effective temperature of 2500 K. Our calculations provide a homogeneous set of evolutionary cooling tracks appropriate for mass and age determinations of old DB white dwarfs and for white dwarf cosmochronology of solar metallicity Galactic populations.