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(1993 Mar. 22)
subject: Request for observations: U Gem
U Geminorum
V-band CCD photometry at Ouda revealed modulation of brightness of
this SS Cyg type dwarf nova during the present bright maximum.
The observation was not long enough, but the star seems to have attained
a maximum at Mar. 20.550 UT and a minimum 20.640 UT. The amplitude of
the modulation of was 0.14 mag. Such variation is common in superoutbursts
of SU UMa type dwarf novae, but seems to be uncommon because orbital humps
usually disappear during outbursts.
The interval between maximum and mimimum was 0.090 day, roughly a
half of the orbital period (0.1769 day). Subesequent visual observations
confirm that this fade was not a part of general decline. It can not be
said at this time whether this modulation represents first-ever-observed
superhumps of U Gem, or other unknown sort of modulation.
From this point of view, we would like to urge photoelectric and CCD
observers to monitor this variable during the current outburst to clarify
the origin of the modulation. Considering the unfavorble location of the
variable for complete phase coverage from one place, co-operated
observations would be essential to determine the period uniquely.
Regards,
Taichi Kato
Return to the Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
