http://arxiv.org/abs/1807.03894
White dwarfs are nowadays routinely used as reliable cosmochronometers, allowing to date several stellar populations. In particular, ultra-massive white dwarfs are involved in other various applications which include physical processes in the Asymptotic Giant Branch (AGB), the theory of crystallization and type Ia supernova explosions. Despite the interest in these white dwarfs, there are few evolutionary studies in the literature devoted to them. Here, we present new ultra-massive white dwarf evolutionary sequences that constitute an improvement over previous ones. In these new sequences, we take into account for the first time the process of phase separation expected during the crystallization stage of these white dwarfs, by relying on the most up-to-date phase diagram of dense oxygen/neon mixtures. Realistic chemical profiles resulting from the full computation of progenitor evolution during the semidegenerate carbon burning along the super-AGB phase are also considered in our sequences. Outer boundary conditions for our evolving models are provided by detailed non-gray white dwarf model atmospheres for hydrogen and helium composition. We assessed the impact of all these improvements on the evolutionary properties of ultra-massive white dwarfs, providing up-dated evolutionary sequences for these stars. These white dwarf sequences provide a new theoretical frame to perform asteroseismological studies on the recently detected ultra-massive pulsating white dwarfs.
M. Camisassa, L. Althaus, A. Córsico, et. al.
Thu, 12 Jul 18
26/60
Comments: 13 pages, 14 figures, 3 tables. Submitted to Astronomy & Astrophysics