On Interacting Helium Star--White Dwarf Pairs as Supernova Precursors

The authors explore the possibility that some Type Ib and some Type Ia supernovae might be the consequence of mass transfer from a helium star to a carbon-oxygen degenerate dwarf. Such mass-transferring systems are formed by close binaries of intermediate mass if the orbital separation is appropriately reduced by common envelope action. If the helium star is kept in contact with its Roche lobe by angular momentum loss due to gravitational wave radiation alone, mass-transfer rates on the order of a few times 10^-8M_sun;yr^-1 arise, and helium is ignited when the mass of the accreted helium shell reaches 0.1 - 0.3 M_sun;. The nature of the outburst depends on the angular momentum of the accreting dwarf and on the abundance of ¹⁴N in the accreted material.