Faint Thermonuclear Supernovae from AM Canum Venaticorum Binaries
Abstract
Helium that accretes onto a carbon/oxygen white dwarf in double white dwarf AM Canum Venaticorum (AM CVn) binaries undergoes unstable thermonuclear flashes when the orbital period is in the 3.5-25 minute range. At the shortest orbital periods (and highest accretion rates, M˙>10-7 Msolar yr-1), the flashes are weak and likely lead to the helium equivalent of classical nova outbursts. However, as the orbit widens and M˙ drops, the mass required for the unstable ignition increases, leading to progressively more violent flashes up to a final flash with helium shell mass ~0.02-0.1 Msolar. The high pressures of these last flashes allow the burning to produce the radioactive elements 48Cr, 52Fe, and 56Ni that power a faint (MV=-15 to -18) and rapidly rising (few days) thermonuclear supernova. Current galactic AM CVn space densities imply one such explosion every 5,000-15,000 years in 1011 Msolar of old stars (~2%-6% of the Type Ia rate in E/SO galaxies). These ``.Ia'' supernovae (one-tenth as bright for one-tenth the time as a Type Ia supernovae) are excellent targets for deep (e.g., V=24) searches with nightly cadences, potentially yielding an all-sky rate of 1000 per year.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2007
- DOI:
- 10.1086/519489
- arXiv:
- arXiv:astro-ph/0703578
- Bibcode:
- 2007ApJ...662L..95B
- Keywords:
-
- Stars: Binaries: Close;
- Stars: Novae;
- Cataclysmic Variables;
- Stars: Supernovae: General;
- Stars: White Dwarfs;
- Astrophysics
- E-Print:
- To appear in The Astrophysical Journal Letters