BELGIAN ASTRONOMICAL SOCIETY V.V.S. -  Working Group Variable Stars
Cataclysmic Variables Circular No.139                  1997, May 12
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
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Var21 CrB [UGSU, 14.5 - <17.5p]
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We received two independent reports announcing the existence of
superhumps in the light curve of Var21 CrB, hence establishing
the SU UMa-type nature of this dwarf nova.

Rudolf Novak, Nicholas Copernicus Observatory, Czech Republic
announced : "We made a 4.08 hours long observing run of Var 21 CrB
on May 11/12 1997. This CVAP listed object shows superhumps with a 
large amplitude (0.4 mag) and a period of approx. 0.0767 +- 0.0001d.
A light curve will soon be placed on VSNET and GAMA home page."

Tonny Vanmunster, CBA Belgium reports : "We obtained 3.3 hours of 
unfiltered CCD photometry of Var21 CrB at CBA Belgium, between 1997, 
May 11.98 UT and May 12.12 UT, using a 0.25-m SCT and ST-7 CCD. The 
light curve clearly shows the existence of superhumps with a semi-
amplitude of 0.17 mag. A preliminary period analysis, using the PDM 
method, yields the following best estimate of the superhump period : 
0.076d +/- 0.001d (short observing window).
Earlier attempts to detect superhumps (between 1997, May 9.89 UT and 
May 10.11 UT) showed only a very weak signal, which could not be 
attributed with confidence to superhumps."

Follow-up observations at different longitudes are highly encouraged.


Tonny Vanmunster