Ultraviolet observations of the long-period dwarf nova DX And in outburst.

Abstract

Ultraviolet observations of the little-studied dwarf nova, DX And, are presented. The observations were made with the International Ultraviolet Explorer satellite during the late stages of a rise to outburst maximum in November 1989. The spectra indicate a low orbital inclination angle and show clear signs of substantial interstellar reddening. The wind-dominated N v 1240 A and C IV 1549 A profiles show significant velocity-shifting within the time series of spectra. If these motions are linked with the binary orbit, an estimate of 11 hr is obtained for the orbital period. Fitting of the C IV and N v absorption profiles provides a lower limit to the mass loss rate of a few times 10 to the -11th solar mass/yr. It is argued that the ionization state of DX And's wind is most probably higher than usual or, failing that, the nitrogen abundance in the accreting material is enhanced.