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Dear colleagues, Joe Patterson (Columbia University, NY) and myself have been working on a first analysis of the GO Com CCD observations, collected so far by the CBA network. Here's an overview of selected intermediate results. Observations have been contributed by Tom Krajci (CBA New Mexico), David Messier, Bob Fried (CBA Flagstaff), Lew Cook (CBA Concord), Jerry Foote (CBA Utah), Donn Starkey (CBA Indiana) and Tonny Vanmunster (CBA Belgium). In total, 1859 observations were included, obtained between JD +2793.5 and JD +2797.8. The data were split in two sets : a first set covers the period JD +2793.5 to JD +2794.8 and the second set JD +2795.1 to JD +2797.8. This corresponds to the precursor outburst stage (first set) and the superoutburst stage (second set). The precursor data reveal no coherent signal (using the PDM technique), as the GO Com modulation is rather weak with an amplitude of 0.1 mag at most. I made several attempts to detect a stable period, but could not conclude. For the second set of data (superoutburst stage), I derived a dominant superhump period value of 0.06288 +/- 0.00009 d (using the PDM technique) and a very stable phase diagram. The average amplitude now was about 0.30 mag. This superhump period value is somewhat different from the one recently reported by the VSNET team (0.06268 d) in vsnet-campaign-dn 3751. I did not (yet) attempt to detect changes in the superhump period, as the time line is still too short. Such an analysis will become more meaningful in the next week, provided that sufficient observations are available. The combined CBA light curve shows exceptionally well the transit between the 2 stages of GO Com's present outburst. A sliced and 'zeroed' version of the light curve, as well as the periodogram and phase diagram for the superoutburst stage are on-line at www.cbabelgium.com. The above analysis tends to confirm most of the findings also reported by the VSNET collaboration team, which is not surprising given the fact that quite a number of CBA observers share their observations also with their VSNET colleagues from Kyoto University. More information about the GO Com analysis is provided on my web site. With the moon now on its way to hamper our GO Com observations, it remains crucial to maintain the intensive coverage, and to continue and study the overall outburst characteristics of this rare cataclysmic variable (cfr the July/August 1995 outburst, which showed a rather complex pattern of outbursts / rebrightenings). With kind regards, Tonny Vanmunster CBA Belgium Observatory www.cbabelgium.com
Return to the Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
