Two New SU UMa-Type Dwarf Novae with Superhump Periods of Over Two Hours: GX Cassiopeiae and V419 Lyrae

Abstract

We succeeded in detecting superhumps in GX Cas and V419 Lyr during the 1994 long outburst and the 1995 outburst, respectively, and identified those stars as SU UMa stars. A period analysis gives 0.09297 (± 0.00005) d as the best-estimated superhump period of GX Cas, which is the third-longest one following TU Men and NY Ser. This superhump period suggests GX Cas to be located at the upper edge of the period gap of dwarf novae. The superhump period of V419 Lyr is estimated to be close to GX Cas, though the short coverage of superhumps prevented us from determining an accurate value. The recurrence cycle of the superoutburst (supercycle) and the normal outburst of GX Cas is estimated to be 386 d and 50–70 d, respectively, based on the VSNET data archive. This supercycle predicts that the next superoutburst in GX Cas will occur around 1998 November 10. Detailed observations of these stars may give important information concerning the study of dwarf-nova evolution as well as the criterion of the tidal instability.