The May 2003 outburst of OU Vir

OU Vir (LBQS 1432-0033) was detected as a cataclysmic variable (CV) of unknown type by C. Berg during the course of his QSO (Quasi Stellar Objects) spectroscopic survey (Berg et al. 1992). During the June 2000 outburst, T. Vanmunster (CBA Belgium Observatory), F. Velthuis and J. McCormick (CBA Pakuranga, NZ) detected superhumps in OU Vir with a period of 0d.078 0d.002 and also found eclipses yielding an orbital period of 0d.07273 0d.00001 [IBVS 4955]. These observations firmly established OU Vir as a genuine eclipsing SU UMa-type dwarf nova. 

The present May 2003 outburst of OU Vir is receiving very good coverage from CV photometrists all over the world, allowing a refinement of our findings published in IBVS 4955. In a VSNET message of May 09, 2003 (vsnet-campaign-dn 3640), T. Kato announced following intermediate results :

"From the superhump period analysis of all the
data up to now, we obtained a preliminary period of 0.0750 d, which is slightly smaller than reported in Vanmunster et al. (2000) IBVS 4955. Combined with the eclipse period, the fractional superhump excess with the new period is 3.1%, which looks like a more acceptable value."

Below, I report my own observations of this intriguing object. I first started monitoring OU Vir on the night of May 6/7, 2003, during a session that lasted for 2.6 hours. The equipment used was a 0.35-m f/6.3 SCT telescope and unfiltered SBIG ST7 CCD camera. The resulting light curve is depicted below. It shows a rather complex modulation, because of the superposition of superhump maxima and eclipses. An eclipse was predicted to occur around JD 2766.470 and is fairly easy to recognize in the light curve. The subsequent one, on JD 2766.543, is much more difficult to distinguish.

The night of May 7/8, 2003 was clear again, and allowed me to monitor OU Vir for about 4.0 hours under relatively good atmospheric conditions. This time, 3 eclipses were recorded and are much easier to recognize in the overall light curve, next to the superhumps.


Although the night of May 10/11, 2003 was not really excellent (cloud fields passing over), we nevertheless set up an unfiltered photometry session on OU Vir, the result of which is shown below. One eclipse was caught towards the beginning of the session, but the other ones were lost due to breaks related to cloud fields. The eclipse depth was about 0.7 mag. The session lasted for 4.5 hours. 





Copyright © 2003 - Tonny Vanmunster.