2 NEW SU UMA-TYPE DWARF NOVAE WITH SUPERHUMP PERIODS OF OVER 2 HOURS - GX CASSIOPEIAE AND V419 LYRAE

We succeeded in detecting superhumps in GX Cas and V419 Lyr during the 1994 long outburst and the 1995 outburst, respectively, and identifie d those stars as SU UMa stars. A period analysis gives 0.09297 (+/-0.0 0005) d as the best-estimated superhump period of GX Gas, 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 d warf novae. The superhump period of V419 Lyr is estimated to be close to GX Gas, though the short coverage of superhumps prevented us from d etermining an accurate value. The recurrence cycle of the superoutburs t (supercycle) and the normal outburst of GX Cas is estimated to be 38 6 d and 50-70 d, respectively, based on the VSNET data archive. This s upercycle predicts that the next superoutburst in GX Cas will occur ar ound 1998 November 10. Detailed observations of these stars may give i mportant information concerning the study of dwarf-nova evolution as w ell as the criterion of the tidal instability.