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KS UMa: full development of superhumps: unusual superhump period! Dear Colleagues, We have received new data from Tonny Vanmunster and the Nyrola team (Arto Oksanen). We have also received the most recent, fantastic data from Nakajima-san, which covered full 6 superhump cycles. The usual observation and analysis of Kyoto team and Torii-san (RIKEN) are also steadily in progress. From these data, the develpment of the superhumps took place on Feb. 19, as already reported. Several hours later, the Nyrola team recorded the growing signal. The amplitude of the superhumps reached 0.25 mag, as Tonny reported. On Feb. 20 later, the amplitude has fully grown to 0.30 mag. From the Feb. 20 observations, the resultant superhump period is 0.07068(7) d, which is substantially longer than the perviously reported periods (see also Tonny's summary in vsnet-campaign-dn 3459). It may be possible that KS UMa is experiencing a stage of rapid evolution of superhump periods, as we have seen in UV Gem early this year. Up to now, such dramatic period changes of the superhumps (except WZ Sge-type early superhumps and trasition in T Leo, Kato (1997) PASJ 49, 583) during the early superoutburst stage have been confined to long-period systems, or systems close to the lower edge of the period gap. If a similar period change (rapid period decrease) is confirmed in KS UMa, this object would become the first object which shows similar evolution of superhump periods as in long-period systems. Further detailed, long coverage is naturally of utmost importance! Regards, Taichi Kato VSNET Collaboration team
Return to the Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
