CI UMa rather bright outburst, recent data
(Possible superoutburst?)
YYYYMMDD(UT) mag observer 20030401.978 <141 (Pavol A. Dubovsky) 20030402.887 <141 (Eddy Muyllaert) 20030402.930 <153 (Gary Poyner) 20030403.865 <141 (Eddy Muyllaert) 20030404.872 <141 (Pavol A. Dubovsky) 20030405.855 <141 (Eddy Muyllaert) 20030406.887 <141 (Eddy Muyllaert) 20030407.883 <141 (Eddy Muyllaert) 20030407.908 <153 (Gary Poyner) 20030408.914 140 (Gary Poyner)
CI UMa definite superoutburst
We have also received a successful report of superhump detection from Tanabe-san team (Okayama U. of Sci.).
YYYYMMDD(UT) mag observer 20030405.855 <141 (Eddy Muyllaert) 20030406.887 <141 (Eddy Muyllaert) 20030407.883 <141 (Eddy Muyllaert) 20030407.908 <153 (Gary Poyner) 20030408.876 141 (Eddy Muyllaert) 20030408.914 140 (Gary Poyner) 20030409.044 143 (Gary Poyner) 20030409.851 140 (Eddy Muyllaert) 20030409.887 138 (Gary Poyner) 20030410.178 141 (Mike Simonsen)
CI UMa observations from Nyrola team
Dear Colleagues,
We have received time-series photometry of CI UMa from Nyrola team (A. Oksanen and P. Tikkanen). The data clearly show 0.2 mag sharp superhumps. We have also received almost nightly observations from Okayama U. of Sci. team, led by Tanabe-san. Since CI UMa has a short superhump period (0.0625 d) and a possibly short supercycle, measuring Pdot is a very important step toward understanding the full picture of superhump period changes in SU UMa stars. Further continious observation throughout the superoutburst are strongly encouraged.
Regards, Taichi Kato
CI UMa superoutburst: period analysis
Dear Colleagues,
The present superoutburst of CI UMa has been covered by Jochen Pietz, Okayama U. Sci. team (Tanabe-san) and VSNET Okayama Station, Hida observatory (Nogami-san) and Ouda station and Kyoto (Ishioka-san and Uemura-san). Although the analysis is still partial, we obtained a greatly refined superhump period of 0.06264(1) d. During the past 60 superhump cycles, the period change has been almost zero, which seems to make a contrast to generally positive Pdot in similar Psh systems with infrequent outbursts (e.g. V1028 Cyg, Psh = 0.06154 d, Pdot = +8.7x10^(-5), Baba et al. 2000 PASJ 52, 429).
Further observations are strongly encouraged to completely follow the evolution of superhumps.
Regards, Taichi Kato VSNET Collaboration team
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
Dear Colleagues,
We have received new complete data sets (five nights) from Jochen Pietz and one night from Nyrola observatory team (Arto Oksanen). The usual data at Kyoto and by Okayama U. of Sci. team are also being analyzed.
The data now clearly shows that CI UMa has entered a rapid decline phase on April 19 (with some hint on April 18). The properties of the superhumps become different since April 17. Before April 17, the period change was almost zero (with a slight tendency of period increase), while the period seems to have made a sudden change around April 17. Late superhumps, however, have not been apparent even in the latest observation, indicating that the sudden change was not associated with a phase 0.5 jump. Futher monitoring for outbursts during the coming one or two weeks is encouraged, since the superhump period of CI UMa is close to those of SU UMa stars with prominent post-superoutburst rebrightenings.
Regards, Taichi Kato VSNET Collaboration team
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