BELGIAN ASTRONOMICAL SOCIETY V.V.S. - Working Group Variable Stars Cataclysmic Variables Circular No.132 1997, April 08 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 =================================================================== DV UMa [UGSU, 15.4v - 20.6v] ============================ Timo Kinnunen, Finland and Tonny Vanmunster, Belgium independently report a visual outburst detection of this most interesting dwarf nova (part of the TA/BAA VSS Recurrent Objects programme). The available observations are : 1997 Apr 07.877 UT, <15.2 (G. Poyner, visual); Apr 07.890 UT, <14.8 (T. Vanmunster, visual); Apr 08.85 UT, 13.9 (T. Kinnunen, visual); Apr 08.931 UT, 14.0 (T. Vanmunster); DV UMa was last seen in outburst on Feb 26, 1995 by Vanmunster [CVC 28]. During that outburst, time-series photometry by the Ouda team at Kyoto University, Japan revealed superhumps with a period of 0.08585 +/- 0.00001 day, a value that is significantly different from the published Porb (0.08579 day). [CVC 29]. Accurate astrometry by Nick James, Chelmsford, UK gave following position of DV UMa : RA = 9h46m36s.64, decl = +44g46'44".8 (J2000.0). This is 2" W and 4" N of the position in 'A Catalog and Atlas of Cataclysmic Variables' [Downes, R.A., Shara, M.M., 1993, PASP, 105, 127-245]. DV UMa was discovered by Usher et al. (1981) as an ultraviolet excess object. The object was subsequently identified as an eclipsing cataclysmic variable by Howell et al. (1988). Their photometric observations showed deep eclipses (1.5 mag or more) with an orbital period of 0.08597 day. Eclipses lasted about 0.15 Porb ~ slightly shorter than 20 min. V795 Cyg [UGSS, 13.4p - <17.9:p] ================================ Lasse Jensen, Denmark and Patrick Schmeer independently detected an outburst of V795 Cyg, which is part of the TA/BAA VSS Recurrent Objects Programme. Several confirmative observations have been received. 1997 Apr 07.010 UT, 13.0: (P. Schmeer, visual); Apr 07.082 IT, 13.4 (L. Jensen, unfiltered CCD); Apr 07.142 UT, 12.7 (P. Schmeer); Apr 08.037 UT, 12.7 (B. Worraker, visual); Apr 08.05 UT, 12.7 (T. Kinnunen, visual); Apr 08.082 UT, 12.6 (G. Poyner, visual); Apr 08.09 UT, 13.1 (T. Vanmunster, CCD); V795 Cyg was last reported in outburst on May 2, 1995 by Vammunster and Jensen [CVC 36]. The present classification of V795 Cyg as a SS Cyg type dwarf nova is partially based on the apparent absence of superhumps in a 1.5 hour CCD photometry run by T. Kato during the November 1992 outburst of V795 Cyg. SX LMi [UGSU, 16B] ================== The SX LMi outburst, announced in our previous circular, is a superoutburst. Unfiltered time-series photometry at CBA Belgium Observatory, using a 0.25-m SCT and ST-7 CCD, on April 7/8 1997 clearly shows the presence of superhumps. A very preliminary analysis of the superhump period yields a best value of approx. 101 min (PDM method) and a mean amplitude of ~ 0.1 mag. CCD photometry at CBA Belgium Observatory on the night before (April 6/7 1997) did not reveal any superhumps, but clearly showed small-amplitude (semi-)periodic oscillations, which very likely are to be interpreted as emerging superhumps. A further comment on the superhump and orbital period of SX LMi was sent to us by John Thorstensen, Dartmouth College : "There's a paper in press by Wagner et al. -- I'm a co-author -- which gives P-orb = 0.06717 +- 1.1 x 10^-4 d, or 96.72 +- 0.16 min, and a superhump period of 0.06893 +- 0.00012 d. The Porb is from spectro- scopy during quiescence ... and the P-superhump is from a few nights of photometry during the 1994 outburst." Since there is still a slight possibility of a cycle-count error, follow-up time-series photometry on successive nights and at various longitudes would be of much value. Further observations of the present outburst : ------------------------------------------- DATE (UT) MAGN MS OBSERVER ------------------------------------------- 1997 03 26.933 15.2: mv Poyner 1997 03 27.021 15.4: mv Poyner 1997 03 28.967 <15.5 mv Poyner 1997 04 02.89 <15.6 mv Kinnunen 1997 04 06.82 13.3 mv Kinnunen 1997 04 06.82 13.6 mv Pietz 1997 04 06.898 13.4 mv Vanmunster 1997 04 06.913 13.9 mv Broens 1997 04 07.82 13.2 mv Kinnunen 1997 04 07.874 13.2 mv Poyner 1997 04 07.892 13.1 mv Worraker 1997 04 07.964 13.3 mv Poyner 1997 04 07.970 13.1 mv Worraker 1997 04 07.997 13.1 mv Worraker 1997 04 08.041 13.1 mv Worraker 1997 04 08.06 13.5 mv Kinnunen 1997 04 08.083 13.2 mv Poyner AQ CMi [UGSU, 14.5p - <16.5p] ============================= Nick James, UK reports some follow-up observations of this interesting object : "I obtained a further image of the AQ CMi field in V-Band last night (April 6, 1997) but the star was not seen to an estimated limiting magnitude of 17.5V. The VSNET star at V17.47 is clearly seen. The latest images are: April 3.886 (15.5V) http://www.astro1.demon.co.uk/images/aqcmi_970403.jpg April 6.865 ([17.5V) http://www.astro1.demon.co.uk/images/aqcmi_970406.jpg " Tonny Vanmunster