IUE observations of the high excitation symbiotic star RW Hya (gM2 + pec) have been obtained. Analysis of the intense UV continuum observed between II00 A to 2000 A suggests this star is a binary system in which the secondary is identified as a hot subdwarf with T _. _I0 D K. We deduce a distance to the system of ~1000 pc. The UV spectrum consists of mainly semi-forbidden and allowed transition lines of which the ClV (1548 A, 1550 A) emission lines are particularly strong, and UV continuum at both shorter and longer wavelengths. Strong forbidden lines seem to be absent suggesting the presence of a nebula of high densities, in the approximate range 10^8 - 10^9 cm^-3. Tidal interaction between the red giant primary and the hot subdwarf is suggested as a likely means to form the observed nebula. RW Hya is suggested as a possible source of soft X-ray emission from material accreting onto the surface of the hot subdwarf. Detection of such emission with HEAO-B ("Einstein") would give us information if this accretion is taking place via Roche lobe overflow or via capture from a stellar wind emitted by the primary. A general discussion of elemental and ionic abundances in the nebula is also presented.
IUE, International Ultraviolet Explorer, high excitation, symbiotic star, UV, ultraviolet, binary stars, subdwarf stars, RW Hya, X-ray, emission lines
Instrumentation | Stars, Interstellar Medium and the Galaxy
Kafatos, M., Michalitsianos, A.G. (1981) IUE Observations and Interpretation of the Symbiotic Star RW Hya. In R.D. Chapman (Ed.), The Universe at Ultraviolet Wavelengths: the First Two Years of International Ultraviolet Explorer. Proceedings of a symposium held at NASA Goddard Space Flight Center, Greenbelt, MD, May 7-9, 1980 (pp. 349-354).