CBA Belgium Observatory
The February 2001 outburst of CP Dra (UGSU)


On 2001, February 23.9340 UT, Christopher Jones (UK) reported a rare, bright outburst of CP Dra (vsnet-outburst 1691). The previous outburst of CP Dra was spotted on 2000, May 15 by Tonny Vanmunster (vsnet-alert 4851). That was a faint and short outburst. CP Dra is located close to NGC 3147, and therefore it is of no surprise that in history, this object has already twice been identified as a possible supernova (in 1914 and 1972). 

I started a CCD photometry session on CP Dra on 2001, February 24/25, using the 0.35-m f/6.3 telescope at CBA Belgium Observatory. FITS images were acquired with an ST-7 CCD camera without filters, and were instantaneously processed and reduced (aperture photometry). 

These observations clearly revealed the presence of a 0.31 mag modulation, to be attributed to superhumps, and thus for the first time established CP Dra as a new member of the UGSU type of cataclysmic variables ! The complete light curve of that night is shown in the figure below.
Following our detection of superhumps in this system, the CBA launched an international observing campaign to densely cover the outburst evolution. Several observers joined us during that campaign and in total, we collected well over 1000 CCD observations.. The complete data set very well shows the transition from initial superhumps at the start of the CP Dra outburst (amplitude of about 0.22 mag), to full-developed common superhumps with a peak-to-peak amplitude of 0.34 mag. The profile of the superhumps was stable over the entire period, and the same was true for the superhump period, which - using the PDM method - yielded a value of 0.08473 +- 0.00006 d. This is value is quite similar to results obtained by the Kyoto Observatory team in Japan.

Arne Henden performed some accurate astrometry on the object and found following coordinates (vsnet-chat 4105) : RA = 10h15m39.85s, Decl =  +7326'05.2" (2000.0)


We are grateful to Denis Buczynski (UK), Marko Moilanen, Brian Martin (CBA Alberta), David Skillman (CBA East), Rudolf Novak 
(N. Copernicus Observatory, Brno, Czech Republic) for their very high-quality observations.


                                                                                                                                          (c) Copyright Tonny Vanmunster, 2001