Observations of the eclipsing nova-like variable Dw Ursae Majoris in a low state

Abstract

We present observations of the eclipsing nova-like variable DW UMa during a previously unseen low state. The continuum is deeply eclipsed and, from measurements of the eclipse width, we deduce that the accretion disc is smaller than during the normal state. In contrast to the normal state, there are no high-excitation emission lines present. The Balmer lines are dominated by strong, narrow emission spikes superposed upon faint wings. The emission spikes originate from the inner face of the secondary star, and the line wings show evidence of an accretion disc origin. We attribute the low state to a decrease in the mass-accretion rate and discuss possible causes of the phenomenon