Nucleosynthesis during the Merger of White Dwarfs and the Origin of R Coronae Borealis Stars

LONGLAND, RICHARD; LOREN-AGUILAR, P.; JOSE, JORDI; GARCIA-BERRO, ENRIQUE; ALTHAUS, LEANDRO G.; ISERN, JORDI

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Año: 2011 vol. 737 p. 34 - 37

0004-637X

Many hydrogen-deficient stars are characterized by surface abundance patterns that are hard to reconcile with conventional stellar evolution. Instead, it has been suggested that they may represent the result of a merger episode between a helium and a carbon-oxygen white dwarf. In this Letter, we present a nucleosynthesis study of the merger of a 0.4 M sun helium white dwarf with a 0.8 M sun carbon-oxygen white dwarf, by coupling the thermodynamic history of Smoothed Particle Hydrodynamics particles with a post-processing code. The resulting chemical abundance pattern, particularly for oxygen and fluorine, is in qualitative agreement with the observed abundances in R Coronae Borealis stars