UV and optical observations of nova Sagittarii 1982.

Abstract

Ultraviolet and optical observations of Nova Sagittarii 1982, are presented and discussed. The light curve and continuum energy distribution give a distance estimate of 4.7 kpc, visual extinction of 1±0.3 mag and M_v(max) = -6.35±0.5 mag. Simultaneous ultraviolet and optical data obtained 4 d after visual maximum, enable to study in detail the continuum energy distribution and emission line spectrum. Such a broad wavelength coverage, during the early decline phase, has never been obtained before. The early decline continuum resembles an early F type spectrum, with effective temperature of ≡9000K. This temperature is too low to explain the strong Balmer emission lines, and the authors discuss another possibility in which Balmer continuum photons provide most of the ionization in H⁺ zone. T > 20,000K photospheric temperatures are indicated, but not directly observed due to the strong optical continuum emitted by the nova shell. The authors discuss also several emission lines in the outer neutral zone, in particular Fe II and [O I] lines. A nebular phase spectrum, obtained 7 months after the eruption, is also shown.