Wednesday, July 31, 2013

1307.7730 (Xin Ma et al.)

A Super-Eddington Wind Scenario for the Progenitors of Type Ia Supernovae    [PDF]

Xin Ma, Xuefei Chen, Hailiang Chen, Pavel A. Denissenkov, Zhanwen Han
The accretion of hydrogen-rich material onto carbon-oxygen white dwarfs (CO WDs) is crucial for understanding type Ia supernova (SN Ia) from the single-degenerate model, but this process has not been well understood due to the numerical difficulties in treating H and He flashes during the accretion. For the CO WD masses from 0.5 Msun to 1.378 Msun and accretion rates in the range from 10^{-8} Msun yr^{-1} to 10^{-5} Msun yr^{-1}, we simulated the accretion of solar-composition material onto CO WDs using the state-of-the-art stellar evolution code of MESA. We found that the properties of H-burning in our accreting CO WD models are similar to those from the steady-state models of Nomoto et al. (2007), except that the critical accretion rates at which the WDs turn into red giants or H-shell flashes occur on their surfaces are slightly higher than those from the steady-state models. Most importantly, the super-Eddington wind is triggered at much lower accretion rates than previously thought when the contributions of nuclear burning and gravothermal energy are taken into account in the total luminosity. This super-Eddington wind naturally prevents the CO WDs with high accretion rates from becoming red giants, thus presenting an alternative to the optically thick wind proposed by Hachisu et al. (1996). Furthermore, the super-Eddington wind can work in low-metallicity environments, which can explain SNe Ia observed at high redshifts.
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