IR Com: Deeply Eclipsing Dwarf Nova Below the Period Gap -- A Twin of HT Cas?

Abstract

We observed an X-ray selected, deeply eclipsing cataclysmic variable IR Com (=S 10932). We detected an outburst occurring on 1996 January 1. The light curve of the outburst closely resembled that of a normal outburst of an SU UMa-type dwarf nova, rather than that of an intermediate polar. Time-resolved photometry during outburst showed that eclipses became systematically deeper and narrower as the outburst faded. Full-orbit light curves in quiescence showed little evidence of orbital humps or asymmetry of eclipses. In addition to the presence of high--low transitions in quiescence, the overall behavior of outbursts and characteristics of the eclipse profiles suggest that IR Com can be best understood as a twin of HT Cas, a famous eclipsing SU UMa-type dwarf nova with a number of peculiarities.