BELGIAN ASTRONOMICAL SOCIETY V.V.S. - Working Group Variable Stars Cataclysmic Variables Circular No.122 1997, January 09 Ed.: T. Vanmunster, Walhostraat 1A, 3401 Landen, BELGIUM Internet: tvanmuns@innet.be TEL. 32-11-831504 CBA Belgium Web Page : http://www.astro.columbia.edu/~cba/be =================================================================== BZ UMa [UGSU:, 10.5v - 17.8v] ============================= Gene Hanson, Arizona, USA reports his detection of an outburst of this interesting dwarf nova (possible SU UMa type). Tonny Vanmunster, CBA Belgium has confirmed the outburst, using a 25-cm f/6.3 telescope and ST-7 (unfiltered) CCD. Available observations : 1997 Jan 08.213 UT, [14.1 (G. Hanson, seq: AAVSO); Jan 09.194 UT, 14.4: (G. Hanson); Jan 09.202 UT, 14.2 (G. Hanson); Jan 09.560 UT, 11.6 (G. Hanson); Jan 09.791 UT, 11.9 (T. Vanmunster, unfiltered CCD image); The previous outburst of BZ UMa was observed by T. Burrows, USA on May 14, 1996 [CVC 94] at mag. 13.7 (brightening to mag. 11.9 in 2.7 hours). It was a normal outburst, that lasted for 4 days only [CVC 96], reaching a maximum magnitude of 10.6. In a recent publication, Ringwald et al. [1] point out that BZ UMa has very infrequent outbursts, lasting 10-20 days, with large amplitudes (delta V approx. 6 mag.). He further notes that superhumps have eluded detection in BZ UMa, but may well exist. He finds an orbital period of 0.0679 days. BZ UMa does have normal outbursts as well as superoutbursts, as can be derived from the long-term lightcurve of BZ UMa, published in [2]. Given the fact that the SU UMa-type nature of BZ UMa is still unclear, and that no superhumps have been detected so far in this system, it is evident that if the present outburst is a superoutburst, it should be searched for superhumps. Close photometric monitoring is of utmost importance ! References ---------- [1] Ringwald, F.A., et al., 1994, MNRAS, 271, 323-342 [2] Jurcevic et al., 1994, PASP, 106, 481. EG Cnc [UGWZ, 11.9v - 17:v] =========================== Further observations of this object are given below. Please continue your monitoring actions, as EG Cnc has sufficiently proven to be quite 'unpredictable'. ------------------------------------------- DATE (UT) MAGN MS OBSERVER ------------------------------------------- 1996 12 19.975 <14.0 mv Jensen 1997 01 03.999 15.70 CU Jensen 1997 01 04.476 13.35 CV Ouda 1997 01 04.871 13.52 CV Ouda 1997 01 05.04 14.1 mv Kinnunen 1997 01 05.906 14.7 CU Vanmunster 1997 01 05.95 15.5 mv Kinnunen 1997 01 06.168 <14.1 mv Shaw 1997 01 06.648 <14.8 mv Itoh 1997 01 07.135 16.04 CU Kiyota 1997 01 07.15 <14.1 mv Kinnunen 1997 01 07.228 <14.6 mv Shaw 1997 01 07.532 <14.3 mv Takahashi 1997 01 07.89 <15.6 mv Kinnunen 1997 01 08.219 <14.1 mv Hanson 1997 01 08.616 <14.8 mv Itoh 1997 01 09.193 <14.1 mv Hanson Tonny Vanmunster