The Nebular Phase of Nova GQ MUSCAE 1983: Evolution of the Ionization of the Optical Spectrum

Abstract

Spectroscopic observations of Nova GQ Muscae 1983 over a period of 4 years during its nebular stage reveal a steady increase in the ionization of the ejected envelope. The forbidden Fe x 6374 A coronal line first appears in the spectrum more than 2 years after maximum, and by the end of the fourth year has become the strongest line in the spectrum. It is shown that the high ionization is caused by photoionization from a hot radiation source with T greater than about 400,000 K whose temperature increases with time. The observations can be explained in the context of the constant bolometric luminosity phase caused by hydrostatic hydrogen burning on the white dwarf remnant. They appear to be an important observational verification of this phase in the nova which is predicted by the thermonuclear model of the classical nova outburst.