TYPE-I SUPERNOVAE AND ACCRETION-INDUCED COLLAPSES FROM CATACLYSMIC VARIABLES

We examine the possibility that the white dwarfs in cataclysmic variables might grow in mass to the Chandrasekhar limit. We demonstrate that the masses of the white dwarfs in classical nova systems generally decrease as a result of nova explosions. We present observational and theoretical evidence in support of the view that the masses of the white dwarfs in recurrent nova systems increase. The critical parameters for which a mass increase is obtained are approximately M(WD) > 1.2 M. and M > 10(-8) M. yr-1. The systems in which the white dwarfs are most likely to reach the Chandrasekhar limit are those which satisfy the above limits on the mass of the white dwarf and on the accretion rate and in which, in addition, the secondary stars are transferring helium-rich material. A subclass of the recurrent novae satisfies all of these conditions. The cataclysmic variable systems in which the white dwarf components can grow to the Chandrasekhar limit are most likely to produce an accretion-induced collapes, rather than a Type Ia supernova. We calculate the rate of these events and find it to be consistent with the birth rate of low-mass X-ray binaries.