10 April 2007 : initial outburst stage of BZ UMa

End of March 2007 and early April so far have provided excellent nights over Belgium. As a consequence, I'm currently flooded by CBA and XO CCD images, coming from the 2 telescopes at CBA Belgium Observatory, working all night long - but you won't hear me complain ;-).

Also the night of Apr 10/11, 2007 was clear. Following the announcement of an outburst of BZ UMa by German amateur astronomer Wolfgang Kriebel (cvnet-outburst), I immediately started a time-series CCD observation session. It lasted for 7.5 hours, covering the initial stage of the outburst of this cataclysmic variable. 

The resulting light curve is quite spectacular : it consists of >500 observations, and clearly shows the rise to maximum light (from mag 14.0 CCDR to mag 13.3 CCDR), dominated by a number of small-amplitude hump-like structures (amplitude of 0.02 - 0.06 mag) and 1 or 2 larger-amplitude "bumps" (amplitude of 0.10 mag). The origin of these irregular and non-periodic features is not at all clear to me. Note that even more spectacular high-amplitude modulations were seen during the April 2004 outburst of BZ Uma - during my observation session of Apr 19, 2004, I observed a 0.76 mag 'flare'.

BZ UMa light curve of Apr 10/11, 2007 - CBA Belgium Observatory

During previous outbursts of BZ UMa, I have also monitored this cataclysmic variable, but so far no superhumps have been seen in this system : Jan 2005, Apr 2004, Feb 2004, Dec 2002.





Copyright © 2007 - Tonny Vanmunster.