New Cooling Sequences for Old White Dwarfs

RENEDO, I.; ALTHAUS, L. G.; MILLER BERTOLAMI, M. M.; ROMERO, A. D.; CORSICO, A.; ROHRMANN, R. D.; GARCÍA-BERRO, E.

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Bristol; Año: 2010 vol. 717 p. 183 - 195

0004-637X

We present full evolutionary calculations appropriate for the study of hydrogen-rich DA white dwarfs. This isdone by evolving white dwarf progenitors from the zero-age main sequence, through the core hydrogen-burningphase, the helium-burning phase, and the thermally pulsing asymptotic giant branch phase to the white dwarf stage.Complete evolutionary sequences are computed for a wide range of stellarmasses and for two different metallicities,Z = 0.01, which is representative of the solar neighborhood, and Z = 0.001, which is appropriate for the study of oldstellar systems, like globular clusters. During the white dwarf cooling stage, we self-consistently compute the phasein 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 releaseof latent heat and the release of gravitational energy due to carbon–oxygen phase separation upon crystallization.We also provide colors and magnitudes for these sequences, based on a new set of improved non-gray white dwarfmodel atmospheres, which include the most up-to-date physical inputs like the Lyα quasi-molecular opacity. Thecalculations are extended down to an effective temperature of 2500 K. Our calculations provide a homogeneous setof evolutionary cooling tracks appropriate for mass and age determinations of old DA white dwarfs and for whitedwarf cosmochronology of the different Galactic populations.