RARE THERMONUCLEAR EXPLOSIONS IN SHORT-PERIOD CATACLYSMIC VARIABLES, WITH POSSIBLE APPLICATION TO THE NOVA-LIKE RED VARIABLE IN THE GALAXY M31

A very bright nova with a peak luminosity significantly larger than the relevant Eddington luminosity might be initiated by a hydrogen shell flash on a very cold low-mass degenerate dwarf accreting matter from a close low-mass companion which fills its Roche lobe in a system with orbital period 80 minutes to 2 hours. Under appropriate conditions, which we calculate, the mass of accreted matter can be as large as 0.005 M. when the explosion occurs, and a luminosity larger than the Eddington limit may be generated by the frictional interaction between the matter in a dense common envelope and the interior stellar cores. The frequency of such explosions in our Galaxy may be about six events per millennium. The most likely precursor is a cataclysmic variable with period near 80 minutes, and the final result of the super nova explosion may be dissolution of the low-mass companion into the escaping high-velocity wind. An outburst that was detected in Andromeda in 1988 may be an example.