A New Model for Progenitor Systems of Type Ia Supernovae

We propose a new model for progenitor systems of Type Ia supernovae. The model consists of an accreting white dwarf and a lobe-filling, low-mass red giant. When the mass accretion rate exceeds a certain critical rate, there is no static envelope solution on the white dwarf. For this case, we find a new strong wind solution, which replaces the static envelope solution. Even if the mass-losing star has a deep convective envelope, the strong wind stabilizes the mass transfer until the mass ratio, q, between the mass-losing star and the mass-accreting white dwarf reaches 1.15, i.e., q < 1.15. A part of the transferred matter can be accumulated on the white dwarf at a rate that is limited to cr = 9.0 × 10-7 (MWD/M☉ - 0.50) M☉ yr-1, and the rest is blown off in the wind. The photospheric temperature is kept around T ~ 1 × 105-2 × 105 K during the wind phase. After the wind stops, the temperature quickly increases up to ~1 × 106 K. The white dwarf steadily burns hydrogen and accretes helium, thereby being able to increase its mass up to 1.38 M☉ and explode as a Type Ia supernova. The expected birth rate of this type of supernovae is consistent with the observed rate of Type Ia supernovae.

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