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[vsnet-obs 563] CVC 38

BELGIAN ASTRONOMICAL SOCIETY V.V.S. -  Working Group Variable Stars
Cataclysmic Variables Circular No.38                   1995, May 22
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
===================================================================

T Leo [UGSU, 10B - 15.7B]
=========================

T Leo is a dwarf nova, which is not included on the CVAP and Recurrent
Objects Programme. It has been studied for a long time, and the behaviour 
of this cataclysmic variable seems to be well understood.

However, recent publications [1,2] indicate that T Leo shows a remarkable
phenomenon after certain outbursts : while returning to its minimum
state, the dwarf nova briefly shows a secondary maximum ('mini-outburst'), 
which can be almost as bright as the primary outburst, but lasts for
only one day or so.

Such mini-outbursts have been seen in other UGSU stars as well. VY Aqr 
showed such an event 22 days after the beginning of a superoutburst [3]. 
WZ Sge appears to have shown a similar event about 30 days after the 
superoutburst began, in all three of its recorded eruptions [1]. The 
origin of this phenomenon is not known, so a close watch on light curves 
for brightenings of this type is most desirable.

Since there is considerable interest in a detailed study of this 'mini-
outburst' behaviour in UGSU variables, we have decided to add T Leo to 
the CVAP, in an attempt to monitor a number of future outbursts intensively 
in order to detect and follow-up mini-outbursts.

A first opportunity to detect mini-outbursts of T Leo might be well on
its way. Patrick Schmeer, Bischmisheim, Germany just reported an outburst 
detection of T Leo. His observation has been confirmed by Tonny Vanmunster, 
Landen, Belgium and Eric Broens, Mol, Belgium, as follows :

1995 05 20.875 UT, [13.6  (P. Schmeer, 0.20-m SCT, seq: Huruhata);
     05 20.958 UT, [13.6  (T. Vanmunster, 0.35-m refl., seq: AAVSO);
     05 21.869 UT,  10.4  (P. Schmeer, 0.20-m SCT, seq: Huruhata);
     05 21.910 UT,  10.2  (T. Vanmunster, 0.35-m refl., seq: TA);    
     05 21.933 UT,  10.4  (E. Broens, 0.35-m refl., seq: TA);   

The previous outburst of T Leo was seen on December 7, 1994 by Patrick
Schmeer. The variable reached mag. 10.5 during that outburst.


References:
-----------

[1] Lemm, K. et al., 1993, PASP, 105, 1120-1126
[2] Bortle, J., 1993, AAVSO CIRCULAR, 268
[3] Patterson, J. et al., 1993, PASP, 105, 69-77

Tonny Vanmunster