SUPEROUTBURST PHOTOMETRY OF AL-COMAE-BERENICES

Photometric observations obtained during the 1995 April - May superout burst of the dwarf nova AL Comae Berenices are presented. This star sh ows rare, large-amplitude outbursts, the last definitely seen in 1975. During the 1995 outburst, as with that of 1961, there was a sharp, tw o-magnitude temporary minimum in the outburst light curve at about 28 days after maximum light. We offer an explanation for such temporary m inima involving the migration of a cooling wave within the accretion d isk. V and I band CCD time-series photometry taken throughout the two- month-long event, reveal a complex period structure with two dominant periods, one near 82 min and one near 41 min. Early in the outburst, p hotometric modulations of 81 and 86 min were seen and are likely to be related to superorbital modulations seen in other large outburst ampl itude dwarf novae. Superhumps developed after similar to 10 days and s how a quasi-stable, nonphase coherent period of 82.5 min. A low-amplit ude 41 min period was present throughout, also appearing not to be pha se coherent. We conclude that the two dominant periods seen are of rel ated origin and we list several possible mechanisms for their cause. P revious quiescence observations of AL Com have shown periods near 87 a nd 41 min. (C) 1996 American Astronomical Society.