New aspects of spectral behavior of SS Cyg and WX Hyi between quiescence and outburst states in the UV

Abstract

We present low-resolution UV spectra of the dwarf novae SS Cyg and WX Hyi in both quiescence and outburst states from observations taken by the International Ultraviolet Explorer (IUE) during the period between 1978–1994 and 1979–1993 for two systems respectively. Both SS Cyg and WX Hyi are characterized by emission lines in quiescence physical states and absorption lines in states of outburst. We concentrated on calculating the line fluxes and line widths of the C IV 1550 Å emission line arising from the disk around the white dwarf of SS Cyg and WX Hyi. We found that there is spectral variability for these physical parameters at different times, similar to that known for their light curves ( Voloshina and Khruzina, 2006; Kuulkers et al., 1991). We attribute it to the variations of both density and temperature as a result of changing the mass transfer rate ( Long et al., 2005; Patterson, 1984; Meyer and Meyer-Hofmeister, 1994; Cannizzo, 2001; Schwope et al., 2002). Also we found that both line fluxes and line widths of SS Cyg are greater than the line fluxes and line widths of WX Hyi.