Cataclysmic Variable in Pegasus

CBET circulars No. 2273 & 2275, issued on May 08, 2010, announces the discovery by Dae-Am Yi (Korea) of an apparent new object (mag about 10.8) on two images taken on May 6.77 with a Canon 5D digital camera (+ 93-mm camera lens). CBET 2275 reports independent discovery of the outburst of this variable by Shizuo Kaneko.

We performed some follow-up of this object remotely through a 0.25-m, f/3,4 reflector + CCD, from GRAS Observatory (near Mayhill, NM).

On our images taken on May 09.4, 2010 we can confirm the presence of an optical counterpart with unfiltered CCD magnitude about 8.5 (UCAC2 Catalogue reference stars) at coordinates:

R.A. = 21 38 06.57, Decl.= +26 19 58.2

(equinox 2000.0; UCAC2 catalogue reference stars).

Our confirmation image:

This is an animation showing a comparison between our image and the archive DSS plate (R Filter - 1991). The archive plates show a close pair of objects at the location of the outbursting variable (GSC 2197:886):

Based upon an examination of the POSS-I and POSS-II plates by Arne Henden (AAVSO), it is possible that the double is composed of two unassociated stars, one with a high proper motion.

Spectrum obtained on May 8.47 UT with the 1.82-m Plaskett Telescope of the National Research Council of Canada, shows strong H-alpha and H-beta in emission (HWFM 800 km/s). Another spectrum obtained using the 1.3-m ARAKI telescope on May 8.66 UT shows a blue continuum and a weak H-alpha emission line, suggesting that the object would be classified as a dwarf nova. (cf. CBET 2275).

According to Taichi Kato (VSNET), given the current brightness (and no known past outburst record), the object may be a large-amplitude WZ Sge-type dwarf nova undergoing a rare outburst!

by Ernesto Guido and Giovanni Sostero