http://arxiv.org/abs/1610.08541
Based on stellar evolution simulations, we demonstrate that rapidly accreting white dwarfs (RAWDs) in close binary systems, like those considered in the single-degenerate progenitor channel of type Ia supernovae, experience recurrent and very strong He-shell flashes in the stable H-burning accretion regime. The He-shell flashes result in the expansion and, utimately, ejection of the newly-accreted material via super-Eddington luminosity winds or Roche-lobe overflow. The white dwarf models do not retain any significant amount of the accreted mass, with a He retention efficiency of < 10% depending on mass and convective boundary mixing assumptions. This makes the evolutionary path of such systems to supernova Ia explosion highly unlikely. Instead, we have discovered that such binary systems are an astrophysical site for the intermediate neutron-capture process. In each of the He-shell flashes H-rich material enters the He-shell flash convection zone. 1D stellar evolution simulations of RAWDs show the H-ingestion flash may not cause a split of the convection zone as it was seen in simulations of He-shell flashes in post-AGB and low-Z AGB stars. We estimate that for the production of first-peak heavy elements this site can be of similar importance for galactic chemical evolution as the s-process production of low-mass AGB stars.
P. Denissenkov, F. Herwig, U. Battino, et. al.
Fri, 28 Oct 16
29/73
Comments: 6 pages, 4 figures, 1 table, submitted to ApJ Letters
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