Article,
The Accretion of Solar Material onto White Dwarfs: No Mixing with Core Material Implies that the Mass of the White Dwarf is Increasing
AIP Advances, 4 (4): 041007+ (Feb 9, 2015)
DOI: 10.1063/1.4866984
Abstract
Cataclysmic Variables (CVs) are close binary star systems with one component
an accreting white dwarf (WD) and the other a larger cooler star that fills its
Roche Lobe. One consequence of the WDs accreting material, is the possibility
that they are growing in mass and will eventually reach the Chandrasekhar
Limit. This evolution could result in a Supernova Ia (SN Ia) explosion and is
designated the Single Degenerate Progenitor (SD) scenario. One problem with the
single degenerate scenario is that it is generally assumed that the accreting
material mixes with WD core material at some time during the accretion phase of
evolution and, since the typical WD has a carbon-oxygen (CO) core, the mixing
results in large amounts of carbon and oxygen being brought up into the
accreted layers. The presence of enriched carbon causes enhanced nuclear fusion
and a Classical Nova (CN)explosion. Thus, the WD in a Classical Nova system is
decreasing in mass and cannot be a SN Ia progenitor. In new calculations
reported here, the consequences to the WD of no mixing of accreted material
with core material have been investigated and the material involved in the
explosion has only a Solar composition. I find that once sufficient material
has been accreted, nuclear burning continues until a thermonuclear runaway
(TNR) occurs and the WD either ejects a small amount of material or its radius
grows to about \$10^12\$ cm and the calculations are stopped. In all cases
where mass ejection occurs, the mass of the ejecta is far less than the mass of
the accreted material. Therefore, all the WDs are growing in mass. (Abridged)
