Origin of the DA and Non-DA White Dwarf Stars

Abstract

Understanding the origin of DA and non-DA stars — the bifurcation of the white dwarf cooling sequence — is one of oldest and perniciously difficult problems in the white dwarf research field. Processes which could play a role have been discussed for years. For example, the idea of diffusive element separation was suggested by Schatzman (1958). The suggestion of convective mixing goes back at least as far as Strittmatter and Wickramasinghe (1971) and Shipman (1972), and this process was actively discussed by a number of authors in the 1970s (see the excellent resume by D’Antona and Mazzitelli 1979).