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摘要
We explore the outcome of mass transfer via Roche lobe overflow of MHe less than or similar to 0.51M(circle dot) pure helium burning stars in close binaries with WDs. The evolution is driven by the loss of angular momentum through gravitational wave radiation (GWR), and both stars are modeled using Modules for Experiments in Stellar Astrophysics (MESA). The donors have masses of M-He = 0.35, 0.4, and 0.51M(circle dot) and accrete onto WDs of mass M-WD from 0.6M(circle dot) to 1.26M(circle dot). The initial orbital periods (P-orb) span 20-80 minutes. For all cases, the accretion rate onto the WD is below the stable helium burning range, leading to accumulation of helium followed by unstable ignition. The mass of the convective core in the donors is small enough so that the WD accretes enough helium-rich matter to undergo a thermonuclear runaway in the helium shell before any carbon-oxygen enriched matter is transferred. The mass of the accumulated helium shell depends on M-WD and the accretion rate. We show that for M-He greater than or similar to 0.4M(circle dot) and M-WD greater than or similar to 0.8M(circle dot), the first flash is likely vigorous enough to trigger a detonation in the helium layer. These thermonuclear runaways may be observed as either faint and fast Ia SNe. or, if the carbon in the core is also detonated, Type Ia SNe. Those that survive the first flash and eject mass will have a temporary increase in orbital separation, but GWR drives the donor back into contact, resuming mass transfer and triggering several subsequent weaker flashes.
- 出版日期2015-7-1
- 单位中国科学院理论物理研究所
