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[vsnet-obs 657] CVC 41

BELGIAN ASTRONOMICAL SOCIETY V.V.S. -  Working Group Variable Stars
Cataclysmic Variables Circular No.41                  1995, June 16
Ed.: T. Vanmunster, Walhostraat 1A, 3401 Landen, BELGIUM
     Internet: tvanmuns@innet.be                  TEL. 32-11-831504
     P. Van Cauteren, de Borrekenslaan 54, 2630 Aartselaar, BELGIUM
     Internet: pvancaut@innet.be                  TEL. 32-3-8774098
===================================================================

BZ UMa [UGSU:, 10.5v - 17.8v]
=============================

Gary Poyner, Birmingham, UK has informed us about an outburst detection
of this interesting dwarf nova, which is part of the Recurrent Objects
Programme (TA/BAAVSS, UK). The observation has been confirmed by Bill
Worraker, Didcot, UK. His observation indicates the object is already
in decline. Available observations :

1995 06 08.986 UT, [13.7  (T. Vanmunster, 0.35-m refl., seq: AAVSO);
     06 09.941 UT, [13.7  (G. Poyner, 0.40-m refl., seq: TA);
     06 10.906 UT, [12.6  (P. Schmeer, 0.20-m SCT., seq: AAVSO);
     06 11.90  UT, [12.6  (P. Schmeer);
     06 14.950 UT,  11.5  (G. Poyner);
     06 15.956 UT,  12.7: (B. Worraker, 0.26-m refl., seq: TA);

According to our records (CVC 18), the last confirmed outburst of BZ UMa 
occurred on October 7th, 1994 (P. Schmeer), when the object reached mag. 
11.1. This was a normal outburst (photometric summary in CVC 19).

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]. The
object further appears in the list of known TOADs, issued by Howell [3].

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.
[3] Howell, S., 1995, AJ, 439, 337-345


KM Lac [UGSS, 14.8p - <17.4p]
=============================

Following the outburst announcement in CVC 40, T. Kato (Ouda Observatory, 
Kyoto University, Japan) communicates : "According to a report of M.Iida
(VSOLJ), who has been monitoring this object by CCD photometry, the object
at the variable designation has been always bright around 14-15 mag....
We do not have enough information to determine if this 14-15 mag star is
really variable, or whether there exists a genuine cataclysmic variable
in its vicinity."

Observers with large telescopes are strongly recommended to add KM Lac
to their observing programme, as to get a better understanding of the
true nature of this intriguing object. For that purpose, KM Lac will
be kept on the VVS - CVAP programme.

Tonny Vanmunster