[vsnet-alert 1190] CVC 151 (USNO 1425.09823278, V1251 Cyg superoutburst)

[Tonny Vanmunster <tvanmuns@innet.be>]

BELGIAN ASTRONOMICAL SOCIETY V.V.S. -  Working Group Variable Stars
Cataclysmic Variables Circular No.151            1997, September 08
Ed.: T. Vanmunster, Walhostraat 1A, 3401 Landen, BELGIUM
     Internet: tvanmuns@innet.be                  TEL. 32-11-831504
     CVC Web Page : http://vsnet.astro.columbia.edu/~cba/cvc
===================================================================

USNO 1425.09823278 [CV:, 13.3R - 19.9R]
=======================================

In addition to the photometry results mentioned in CVC 149, we
report another night of CCD observations of this object at CBA
Belgium Observatory. A photometry run of 4 hours on the night of
September 6/7, 1997 again yields a weak periodic signal, which we
believe might be the superhump. A PDM analysis of these results,
combined with the 6 hours run described in CVC 149, gives a
period of 0.057 +/- 0.001 d, which is identical to the value
mentioned in CVC 149. The mean semi-amplitude of the signal was 
0.028 mag.

Assuming this period corresponds to the superhump period, this 
would classify USNO 1425.09823278 among the shortest Psh SU UMa
stars, making it either a WZ Sge or ER UMa - type dwarf nova.

Rudolf Novak, observing at Nicholas Copernicus Observatory in the
Czech Republic, also reports CCD observations, obtained during
the night of September 7/8, 1997. A PDM analysis of his data
yields a periodic signal at 0.07 +/- 0.01 d, a value which is not
entirely consistent with the one mentioned above. 

It therefore seems very likely we will have to wait for another 
bright outburst of this intriguing object, before we can decide 
upon its precise nature and possible superhump period. Unless of 
course, the object rebrightens in the coming days ...



V1251 CYG [UGSU, 12.5p - <15p]
==============================

The V1251 Cyg outburst, detected by Poyner and Kinnunen [CVC 150],
appears to be a superoutburst. Unfiltered CCD photometry at CBA 
Belgium Observatory by the undersigned, on the night of Sep 7/8, 
1997, during a 5.3 hours run, clearly shows the existence of
superhumps. Using the PDM method, we derive a superhump period
of 0.075 +/- 0.001 d, a value which is consistent with the one
published by Taichi Kato [CVC 150]. The superhump semi-amplitude
was only 0.04 mag, suggesting the outburst has just started.
Follow-up observations, preferably through high-speed photometry, 
are therefore encouraged.

Both the 1991 and 1994 outbursts of V1251 Cyg were superout-
bursts too. It appears no normal outbursts ot his object have been 
observed yet.


Tonny Vanmunster

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