Red component activity in dwarf novae

Abstract

SU Ursae Majoris systems are short-period binary dwarf novae characterized by two distinct classes of outbursts: ‘normal outbursts’ of duration ∼2 days and less frequent ‘superoutbursts’ which last ∼12 days. Superoutbursts may be present in longer-period systems but could be classified as wide outbursts1. Superoutbursts require enhanced mass transfer rates for an extended period of ∼10 days to explain their sustained activity2,3. During superoutbursts, ‘superhumps’ are observed4–6 which modulate the visible light by ≲40% with a period 3–7% longer than the binary period. Measurement of eclipse depths in the two eclipsing SU UMa systems during superoutburst should show whether or not the superhump light is eclipsed and hence make it possible to infer its location either in the eclipsed disk or in the uneclipsed red component. Study of the available eclipse data reported here shows that the superhump light is not eclipsed, so that the red component is the location of the superhump.