[vsnet-alert 10027] SY Cap: definitely a dwarf nova

[Denis Denisenko]

Dear all,

I have checked Skymorph database (S. Pravdo et al.) and found 4 
outbursts of SY Cap in archival NEAT images:

1996-09-10
2001-05-08 (same as JD=2452040 ASAS outburst)
2002-09-21 (fainter on 2002-09-23)
2006-06-30

There are 149 images available for 52 different dates, with star being 
in outburst on 5 dates ("duty cycle" of about 10 per cent).  Outbursts 
are as bright as 13.5CR using USNO-A2.0 0675-35495524 (R=13.3, B=14.3) 
as a comparison star.

SY Cap is present in USNO-A2.0 catalogue with the following magnitudes: 
R=18.2, B=18.2.
USNO-B1.0 mags are B1=18.77, R1=18.43, B2=18.81, R2=17.72, I=17.74.
2MASS gives J=16.33+/-0.15, K=15.45+/-0.24 for 2MASS 20294753-1554374.

Thus, SY Cap is definitely not a Mira - it is a cataclysmic variable 
indeed!  Anybody having access to 1-meter telescope might try to measure 
the orbital period even at quiescence.

Color-combined BRIR finder chart is available at 
http://hea.iki.rssi.ru/~denis/SYCap-comps.gif (10'x9' FOV, 114 kB)

Denis in Moscow

Taichi Kato wrote:

> I noticed that SY Cap (GCVS M:) is almost certainly a dwarf nova.
> ASAS-3 recorded several outbursts. The most recent one in 2007 Sep
> (max 13.0) looks like a superoutburst. Several similar outbursts
> were also recorded. Please put this on your CV monitoring list.