The ultraviolet variability of the symbiotic star HBV 475.

Abstract

Evidence is presented for the binary nature of the symbiotic star HBV 475 ( = V 1329 Cyg), based on ultraviolet observations taken with the International Ultraviolet Explorer. The fluxes in the emission lines and in the continuum observed during 1978-1982 are related. It is found that the changes in the line and continuum fluxes observed in the far ultraviolet (1200-3200 A) are consistent with the 950 d period found from the visual luminosity variations. Periodicity and amplitudes found in the wavelength shifts are shown to indicate a size of the binary system of approximately 2 x 10 to the 14th cm. The emission lines are found to originate in a radiatively ionized gas with electron density in the range of 10 to the 6th to 10 to the 7th/cu cm, and electron temperature less than 15,000 K. In addition, an indication for a hot outer envelope around the whole system is observed.