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CI UMa: further observation by the VSNET Collaboration Dear Colleagues, The current superoutburst of CI UMa has been almost nightly followed by the VSNET Collaboration. We have further received/analyzed new data from Nogami-san (Hida observatory), Uemura-san (Ouda station), Tanabe-san (VSNET Okayama Station) and Okayama U. of Sci. team, and Kyoto observations (Ishioka-san). On April 15, the superhump maxima was sometimes composed of two separate peaks. On April 16, this feature apprarently disappeared. From the superhump timing analysis, there has been only very little superhump period change (there has been a slight tendency of a positive period derivative). This virtually zero period derivative may either be a result of the borderline location of the CI UMa superhump period (Psh = 0.06264 d), or a result of a differerent mechanism (e.g. pressure effect) as proposed in BF Ara (Kato et al. MNRAS in press, astro-ph/0301565). Since the observed |O-C| have been within 5 minutes, further accurate measurements of superhumps are very strongly encouraged. Regards, Taichi Kato VSNET Collaboration team
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