Will a Supernova explode in CD-30°11223?

Abstract

Accretion of He-rich matter onto a low-mass CO WD from a He-rich donor may lead to an explosive event of SN Ia proportion, though with low peak luminosity and peculiar nucleosynthesis. Recently such a possibility for some binaries with He-accreting WDs has been questioned, suggesting that, if the effects of rotation are accounted for in the evolution of the accretor, the latter does not explode, but it becomes a WD with a massive He-buffer. We investigate the expected evolution of the currently detached binary CD-3011223 harboring a 0.74Msun CO WD and a 0.47Msun donor with a He-burning core and a very thin H-envelope. We use the stellar evolution code FuNS to compute the evolution of CD-3011223 up to the epoch when the two components come into contact and through the RLOF phase of the donor. With respect to our earlier study of the system PTF J2238+743015.1, we also include the transport of angular momentum due to magnetic instabilities (magnetic model). During the H-accretion phase, the effects of rotation in the accretor are negligible. In the "magnetic model", the angular momentum deposited by the accreted matter is very efficiently redistributed along the whole WD due to magnetic instabilities, so that the angular velocity of the accreted layers remains very low. During the He-accretion phase, the accretor experiences two very strong He-flashes, which result in the ejection from the binary system of a large part of the matter previously accreted. The system ends its life as a CO core capped by a massive He/C/O-envelope (Delta M_env ~ 0.194Msun) and an extremely low-mass companion, remnant of the donor, like in a rotating model not including the effects of magnetic field. The system CD-3011223 cannot be regarded as the potential progenitor of Supernova Ia. Such a conclusion applies also to all detached binary systems having similar masses of components and orbital periods.

arXiv comment10 pages, 8 figures, Accepted for the publication in Astronomy & Astrophysics