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THE ASTRONOMER Electronic Circular No 2644      2010 May 09 12.13UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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POSSIBLE NOVA OR NEW CATACLYSMIC VARIABLE IN PEGASUS
Further to TA E-Circular 2643, an independent discovery by Shizuo Kaneko 
of Japan at magnitude 9.0 on 2010 May 7.78UT has been reported on CBET 
2275. Nakano has obtained a precise position from this image of:
RA 21h 38m 07.03s DEC +26 20'03.0"(2000), adding that a magnitude 14 
star is visible at positional end figures RA 11.5s, DEC 01".

K. Itagaki, Japan, has an image of May 1.71 UT with a 0.21-m telescope, 
which suggests that the star was then at a quiesient phase near 
magnitude 15 with end figures 06.66s, 19'57.1". This suggests it is the 
southern component of the GSC star mentioned on TA E-Circular 2643.

Arne Henden, AAVSO, notes that Palomar Sky Survey (POSS) plates show a 
close pair of objects at the location of the outbursting variable:  one 
is essentially stationary, while the other has a relatively high proper 
motion. On the POSS-I plates, the southwest component of the 
3"-separated double is obviously blue, while on the POSS-II plates, it 
has moved east-northeast by about 3" and is now about 1" southeast of 
the stationary northeast component.
At this motion rate, it would be expected to lie an arcsec or two east 
of the stationary component at this epoch.  This rate of motion would 
imply something intrinsically faint but relatively close; adding in the 
colour would imply a white dwarf -- suggesting that the moving object is 
the outbursting object and that it is a cataclysmic variable with an 
amplitude of about 6 magnitudes.

A. Arai, Kyoto Sangyo University, reports that an optical spectrogram 
obtained using the 1.3-m ARAKI telescope on May 8.66 UT shows a blue 
continuum and a weak H-alpha emission line (EW about 0.4 nm), suggesting 
that the object would be classified as a dwarf nova.

In a separate VSNET message Dr. Boris Gaensicke, Associate Professor, 
Department of Physics, University of Warwick relays that
the Pegasus object has been detected in the GALEX All-Sky Survey in 
quiescence (MJD=53955.8). Measurements suggest it resembles an outburst 
of a WZ Sge star. The ultraviolet spectrum of WZ Sge stars is dominated 
by emission from the white dwarf photosphere. The flat ultraviolet 
spectrum is compatible with a white dwarf temperature of ~15000K, 
similar to that of WZ Sge itself. Assuming a 0.6Msun white dwarf mass, 
the GALEX fluxes imply a distance of ~70pc. It appears now most likely 
it is indeed a WZ Sge star, i.e. a short-period cataclysmic variable 
with a low accretion rate and rare but large-amplitude outbursts, and it 
might be among the closest known members of this class.

Guy M Hurst