Outburst Characteristics in the Dwarf Nova SU Ursae Majoris

The 1973-1999 V-band light curve from AAVSO visual estimates and RoboScope CCD exposures is examined to study the systematic properties of normal outbursts and superoutbursts in this prototype of the SU UMa-type dwarf novae. A number of the outbursts' correlations previously reported in VW Hyi and in SU UMa are not present in these data. Several lines of evidence suggest that, during this 26 year interval, variations in the mass-transfer rate served to obscure some of the expected correlations. The M variation apparently caused a nearly complete cessation of outbursting in 1980-1983. We do find a correlation of the time since the last superoutburst with the mean brightness in the interval since the last superoutburst, supporting the notion that superoutbursts are a disk-initiated phenomenon that occurs when the gas remaining in the disk after each normal outburst has accumulated to some critical value.