The recurrent novae and their relation with classical novae

Recurrent novae (RNe) are a subclass of cataclysmic variables classified based on recorded observations of more than one nova outburst. They form a small, but heterogeneous group of objects, with 10 known members, that undergo classical nova-like outbursts, with the significant differences being in the amplitude and the frequency of the outbursts. RNe outbursts are of smaller amplitude with lesser energy released as compared to the classical novae. The outbursts occur with intervals of similar to 10 - 100 yr. Some RNe systems are short period binaries similar to the classical novae, while other members of this group are long period binaries, with orbital periods of the order of several hundred days and consist of a hot white dwarf and a rod giant similar to the symbiotic stars. It is widely believed that the white dwarfs in RNe are massive and close to the Chandrasekhar limit. The mass transfer rate from the companion is high, of the order of similar to10(-7)M(circle dot) yr(-1). The massive white dwarf and the high mass-transfer rates, and the nature of the companion (in some systems) are responsible for the differences in the observational properties between RNe and the classical novae.