Detection of the UGSU-type nature of 
optical transient OT_J021110.2+171624 

On Jan 30th, 2008, Patrick Wils (Belgium) reported on cvnet-discussion the detection by the Catalina Sky Survey of an optical transient of mag 14.3 on Jan 29th, that was suspected to be an outburst of USNO-B1.0 1072-0031053 (position RA = 02:11:10.19, Decl = +17:16:24.4, J2000.0) , a star which is normally R=19.2. Patrick furthermore reported that brightenings were not seen on NEAT images, but the object appeared bright on 2 out of 9 POSSII images (a blue image from 1987.94 and a red image from 1990.88, while it was faint on red images 1 and 2 months before). 

Following Patrick's announcement, I started unfiltered CCD time-series observations of the new OT at CBA Belgium Observatory on Jan 30.833 UT, 2008, using a 0.35-m f/6.3 telescope and ST-7XME CCD camera. Sky conditions were good, and the session lasted for 2 hours. The resulting light curve is presented below and shows a superhump-like structure with an amplitude of 0.15 mag. Given the short duration of the session, it's difficult to accurately establish the hump period. Using Peranso's implementation of the ANOVA method, I find a value of 0.06 +/- 0.01 d. 

Light curve of OT_J021110.2+171624, after removing a linear trend of decline. 
The object was observed through a 2.3 airmass towards the latter part of the session.

A few days later, Prof. Joe Patterson, Columbia Univ. NY, reported more detailed period analysis results, combining observation from CBA members Bob Koff, Jerry Foote, Tut Campbell and myself. Patterson reported large amplitude superhumps with P=0.0897(4) d. The above observations establish OT_J021110.2+171624 as a new UGSU-type dwarf nova





Copyright © 2008 - Tonny Vanmunster.