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[vsnet-obs 5615] S 10932 COM eclipse data

Dear colleagues,

I performed 5.6h of unfiltered CCD photometry on RX J1239.5+2108 = 
S 10932 COMAE BERENICES last night (Apr 23/24, 1996), using the 0.25-m 
SCT at CBA Belgium Observatory.

The resulting photometric data show three successive eclipses, with
an average amplitude of 1.2 mag, which is quite low compared to
results published in CVC 135, and a average duration of 10 - 11 minutes.

I furthermore calculated mid-eclipse times (heliocentric corrected),
using a least squares method on a third degree polynomial fit, and
compared the observed times with calculated ones (O-C), based on
the ephemerides published in CVC 135. 

I was quite surprised to note a significant difference, the average
O-C value being -0.0038 d or nearly -5.5 minutes. Please note that I 
calibrate my PC clock before the start of each observing session.

I would very much like to learn about mid-eclipse timings performed at
other observatories, during the present outburst. It is hard to believe
that S 10932 Com's eclipses would have changed so dramatically since the
previous outbursts.

My data also show that this star exhibits quite significant flickering
(up to 0.4 mag). During the observing session, S 10932 faded by
0.04 mag / hour. 

A rough inspection of tonight's CCD data (Apr 24/25), shows that the outburst 
is still ongoing. However, the object has become very faint now (a rough 
estimate from LCD screen : mag 16.5).

Kind regards,
Tonny Vanmunster
CBA Belgium Observatory