2010A&A...523A...3L

The recent discovery of several overluminous type Ia supernovae (SNe Ia) indicates that the explosive masses of white dwarfs may significantly exceed the canonical Chandrasekhar-mass limit. Rapid differential rotation may support these massive white dwarfs (WDs). Based on the single-degenerate scenario and assuming that the WDs would differentially rotate when the accretion rate {dot}(M)>3x10^–7M_☉/yr, we performed the numerical calculations for ∼1000 binary systems consisting of a He star and a CO WD with Eggleton's stellar evolution code. We present the initial parameters in the orbital period - helium star-mass plane (for WD masses of 1.0M_☉ and 1.2M_☉, respectively), which lead to super-Chandrasekhar mass SNe Ia. Our results indicate that for an initially massive WD of 1.2M_☉, a large number of SNe Ia may result from super-Chandrasekhar mass WDs. The highest mass of the WD at the moment of the SNe Ia explosion is 1.81M_☉, but very massive (>1.85M_☉) WDs cannot be formed. However, when the initial mass of WDs is 1.0M_☉, the explosive masses of SNe Ia are nearly uniform, which is consistent with the rareness of super-Chandrasekhar mass SNe Ia in observations.