January/February
2003 observations of GZ Cnc
Below is an overview
of (unfiltered) CCD observations of GZ Cnc,
collected at CBA Belgium Observatory in January
& February 2003. Equipment used was a
0.35-m f/6.3 SCT telescope and SBIG ST-7 CCD camera.
My first night of
observations was January 30/31, 2003, when sky
conditions were quite bad, with only short breaks
between long spells of clouds. The resulting light
curve nevertheless confirms the findings of the
VSNET Collaboration team (vsnet-campaign-dn 3376),
who noticed large-amplitude humps with a
superhump-like profile, next to short-period
modulations with a low amplitude.
The night of January 31/February 01,
2003 had better atmospheric conditions, with
long and stable clear periods. The variable was
monitored for 6.0 hours, and the resulting light
curve is amongst the most interesting, but also most
complex ones I have seen in months (see below). At
the beginning of the session, GZ Cnc was fading by
about 0.5 mag, as part of what seemed to be the
slope of a superhump. The subsequent rise showed a
first remarkable and symmetric dip of about 0.35 mag
around JD +2671.46. Apparently, this was the start
of a gradual brightening of the object, which
continued till the end of the session. However, this
rising trend was superimposed with lots of irregular
and short period oscillations about 0.1 - 0.2 mag in
amplitude. Large amplitude modulations started to
appear again in the light curve around JD +2671.57,
when GZ Cnc showed an amazing, eclipse-alike 0.8
magnitude drop. After that, high amplitude
variations continued to exist until the end of my
observing session. What a nice show this variable
puts on !