2003 superoutburst of GO Com
June 2, 2003, Hazel McGee (UK) reported her visual
detection of a rare and bright outburst of the
large-amplitude cataclysmic variable GO Com. This
object was discovered by Kowal as an eruptive object
on a Palomar plate taken on July 1.213, 1977. The
variable was confirmed to be identical to the
suspected variable star CSV 1959 = SVS 382
(Belyavskij 1933). In 1981, Usher independently
discovered a very blue star of B=18.1, during his
survey of the North galactic pole region, that
afterwards was identified to be GO Com. Vogt and
Bateson (1982) classified GO Com as a UGWZ-type
dwarf nova, based on its large outburst amplitude
and low outburst frequency.
GO Com had
not been seen in outburst anymore since April 1998.
Before that date, GO Com was reported to be in
outburst on 1997, Feb 07 [CVC 128] and on 1996, Mar 26 [CVC 89].
The latter was a faint, normal outburst. GO Com underwent a very remarkable series of outbursts in July/August
1995. In less than one month, 3 separate outbursts were
- The first outburst of GO Com was detected on July 16, 1995 (T.
Vanmunster) [CVC 47]. I estimated the object at mag. 13.3. Due to the low altitute of GO Com at the moment of outburst detection, no confirmative observations were received.
- Hungarian amateur Laszlo Szentasko detected the second outburst of GO Com. His observation (mag. 13.3) was made on July 30, 1995 [CVC 51].
- It is still unclear how the exact relationship between het first and second outburst of GO Com should be interpreted.
Likely, the first outburst was a normal one, triggering the second (super?)outburst ? To make things even more complicated, another outburst was reported, about two weeks later. This third one was detected by Daisaku Nogami and Taichi Kato, Ouda Team, Kyoto University, Japan on August 13, 1995 [CVC 52], when they observed GO Com at mag. 15-15.5.
Due to the bad visibility
of GO Com in 1995, this outburst did not allow
detailed CCD photometry to study the outbursting
characteristics cq. detect superhumps.
Final confirmation of
the SU UMa-type nature of GO Com came on June
5, 2003, when Tom Krajci (CBA Uzbekistan)
announced the detection of superhumps with an
amplitude of 0.3 - 0.4 mag. By that time, the object
had just left the precursor outburst stage, and
entered into the superoutburst stage.
GO Com is now the subject of an intensive CCD
monitoring campaign (VSNET, CBA), resulting in
excellent coverage of each stage of the outburst.
For a detailed analysis of the CBA observations of
GO Com, click here.
initial superhump period determination by Tachi Kato
[vsnet-campaign-dn 3738] results in a value of 0.06327(11)
is well in agreement with photometric quiescence
observations of GO Com by Steve Howell, Paula Szkody
a.o. (PASP, 102, 758-772, 1990), on the basis of
which they determined a 95-min period, assumed to be
the orbital period.
I here report my own
observations, obtained at CBA Belgium Observatory,
using the 0.35-m f.6.3 telescope and unfiltered ST-7
I first observed GO
Com in the night of June 5/6, 2003, under good
atmospheric conditions. The variable was monitored
for 4.1 hours, and the resulting light curve is
shown below. Superhumps with a 0.25-mag amplitude
are obvious, and result in a superhump period
(determined using the PDM technique)
of 0.0635 +/- 0.0003 d.
On June 06/07, 2003, I had another unfiltered CCD run on GO Com.
Sky conditions were not really good (quite hazy), and the session was
limited to 2.5 hours. The unfiltered mag of GO Com was about 13.6.
The resulting light curve (see below) shows the presence of superhumps with an amplitude of 0.24 mag.
a 4.0 hours unfiltered CCD session of GO Com. The
unfiltered mag of GO Com was
about 13.7 (0.1 mag fainter than yesterday). The
resulting light curve is shown below.
Although it still clearly shows
superhumps, their amplitude definitely has become
smaller compared to previous nights (it
is now about 0.16 mag). The
trend of decline (0.1 mag in 5 hours), reported by Tom
Krajci (CBA New Mexico) in vsnet-campaign-dn
3755, is confirmed by my observations, but seems to
have slowed down a bit.
Another clear night (2003, June 07/08) over CBA