Ultraviolet comparison of normal outbursts and a supermaximum in two dwarf novae.

Abstract

IUE spectra of AY Lyr obtained shortly after supermaximum and normal maximum and of RX And after normal maximum are compared. All spectra are compatible with steady state disk models in the ultraviolet while the declining stages show an upturn in flux longward of 2500 A which indicates the presence of a cool component. For the same optical magnitude, the ultraviolet flux of AY Lyr is a factor of two higher after supermaximum than normal maximum, implying a larger accretion rate during supermaximum. The lines of RX And exhibit P Cyg profiles which diminish during the decline. The terminal velocities right after maximum are greater than the escape velocity but then decrease rapidly along with the column density by the third day after maximum light has ended.