STUDIES OF CLASSICAL AND RECURRENT NOVAE

Abstract

ABSTRACT Novae belong to the cataclysmic-variable class of objects. 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 disk that surrounds the primary, which, in most cases, is a white dwarf. A nova outburst is caused by a thermonuclear runaway on the surface of the white-dwarf primary. In this study we present optical spectroscopy data of the classical novae LW Serpentis 1978, V443 Scuti 1989, and the recurrent nova RS Ophiuchi 1985, obtained during outbursts, and spectroscopic data of the recurrent novae T Coronae Borealis, RS Ophiuchi, and T Pyxidis, and the classical nova GK Persei 1901 obtained during quiescence. Also presented are the images of the shells of GK Persei and T Pyxidis in H-alpha + [N II] and [O III] emission lines. Most of the data used in the study were obtained with the 102-cm telescope at the Vainu Bappu Observatory. In addition, we also used data obtained at the European Southern Observatory and archival data on RS Ophiuchi from the International Ultraviolet Explorer. The following were obtained from the analysis of the data: (i) Estimation of the electron density in the expanding ejecta following the outburst, temperature in the forbidden/coronal line-emitting region, helium abundance, and effective temperature of the ionizing source. (ii) Estimation of the spectral type of the secondary, the spectrum of the accretion disk, the accretion rate, effective temperature of the ionizing source, and the electron density in the accretion disk, based on the spectra during quiescence. (iii) Detection of the secular, orbital-phase dependent variation in line emission from T Coronae Borealis, based on extensive data (1985-1990) obtained during quiescence. (iv) Detection of a bimodal distribution in the proper motions of hte shell in nova GK Persei.