The ultraviolet spectrum of the symbiotic star HM Sge.

Abstract

The authors present IUE fluxes of the symbiotic star HM Sge, extracted from IUE observations made during the years 1978 - 1983. They argue in favour of an accretion disc model. They suggest that the sudden flux increase in He II and the more highly ionized atoms were due to a decrease from a high mass accretion rate, leading to a luminosity above the Eddington limit, to a lower rate leading to a luminosity below that limit. A thermonuclear runaway model might, however, present an alternative. For elemental abundances it is found that by number He/H = 0.14, that within the uncertainty limits, the oxygen and neon abundances are essentially solar, with a slight overabundance of carbon and silicon, and nitrogen is enhanced by approximately a factor 8. Contrary to an occasionally stated opinion the authors do not believe that HM Sge should be associated with a Wolf-Rayet star.