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KS UMa: drastic change in superhump profile! Dear Colleagues, We have receive a large amount of KS UMa observations from Jochen Pietz (two nights), Tonny Vanmunster (two nights), Brian Martin, Maehara-san, Kyoto team and Torii-san. The entire analysis is keenly in progress. A preliminary analysis of the data indicates that there has been a drastic change in the superhump profile between Feb. 23 and Feb. 24. In the late Feb. 23 - early Feb. 24 data, the main superhump maxima become weaker, while other peaks (secondary superhumps and other peaks) became stronger. The profile has now become very complex, which resembles that of superhumps during the rapid decline stage. However, the present stage (only 4 days since the appearance of superhumps) is too early for such a rapid decline, neither observations show such a rapid trend. In some short-period SU UMa stars, there sometimes happen a stage of reduced superhump amplitudes during the late course of a superoutburst (see V1028 Cyg, Baba et al. (2000) PASJ 52, 429), which is probably not the case. A remaining possibility is that KS UMa is exhibiting a early-stage phase transition, as observed in ER UMa (~5 days after the superoutburst maximum, see Kato et al. (2002) PASJ in press, astro-ph/0211520 or vsnet-preprint 106). If such a transition is indeed confirmed in KS UMa, the present detection would make the first case of such transitions other than ER UMa-type dwarf novae. Further long time-series observations are undoubtedly needed! The mean superhump period up to now is 0.07014 d, with a likely stepwise period decrease (analysis in progress). Regards, Taichi Kato VSNET Collaboration team
Return to the Powerful Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
