Novae

Novae belong to the group of cataclysmic variables. These objects are interacting binary star systems consisting of a Roche-lobe filling secondary,on or near the main-sequence, losing hydrogen rich material through the inner Lagrangian point onto an accretion disc that surrounds the white dwarf primary.The matter accreted by the white dwarf reaches a critical amount, the temperature at the base of the envelope rises sufficiently to ignite thermonuclear reactions, which lead to a runaway reaction. This thermonuclear runaway results in the explosive ejection of the accreted material causing a nova outburst and an increase in the brightness ranging from 7 - >14 mag. The envelope is ejected with velocities > 300 km/s. Some novae are found to have repeated outbursts, with outburst intervals of the order of decades. These are termed as the recurrent novae. The white dwarf in most of these systems are believed to be massive, with the mass close to the Chandrasekhar limit, and hence could be potential progenitors of supernovae of type Ia.

The studies of novae at IIA consist of spectroscopic follow-up of a nova outburst with an attempt to understand the temporal evolution of the physical conditions of the expanding envelope. Observations of novae at quiescence provide information about the binary system and the accretion phenomenon, which is of particular interest in the case of recurrent novae. They also provide information about the geometry of the ejected envelope, and a means to study the immediate environs of the system. The study of nova remnants is also done in the radio using the GMRT.