ASAS-SN Discovery of a Bright Optical Transient Near PGC 065535

ATel #5209; K. Z. Stanek, B. J. Shappee, C. S. Kochanek, J. Jencson, U. Basu, T. Haloien, J. F. Beacom (Ohio State), J. L. Prieto (Princeton), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), M. Dubberley, M. Elphick, S. Foale, E. Hawkins, D. Mullens, W. Rosing, R. Ross, Z. Walker (Las Cumbres Observatory), J. Brimacombe (Coral Towers Observatory)
on 16 Jul 2013; 16:53 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

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During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"; ATel #5138, #5168, #5177, #5183, #5186, #5193), using data from the double 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, possibly a bright supernova or a CV in outburst:

 
Object       RA (J2000)    DEC (J2000)     Disc. UT Date   Approx. Disc. V mag 
 
ASASSN-13bq  20 51 13.447 -18 38 52.63     2013 7 16.45     15.0 

No source is detected on 7/14 or in earlier images (V>17 mag), with initial strong detection in two ASAS-SN images on 7/16, followed by confirmation detection still the same night (3.7 hours later) on another four images, giving consistent magnitude estimate. See the ASAS-SN discovery image, top left panel shows the reference image, top right shows the DSS image on the same angular scale, lower left is one of the 90-sec V-band images on 07/14 and lower right is the first detection image on 07/16. Circle with the 15" radius has the same position.

The new source is approximately 71.2" South and 73.1" East of the center of z=0.020257 (86 Mpc) galaxy PGC 065535, giving it an absolute magnitude of approximately M_V=-19.8 (m-M=34.7, A_V=0.16, Schlafly & Finkbeiner 2011) and a projected distance from the galaxy center of approximately 41 kpc.

However, close to our position, about 8" away, there is a faint USNO-B1.0 source with B=21.4, but fairly red colors. A faint source is also present 7" away in the CRTS catalog, but it shows no significant previous variability. These two datum argue somewhat against ASASSN-13bq being a CV in an outburst. Follow-up spectroscopy to determine the nature of this source is strongly encouraged.

For more information about the ASAS-SN project, see this link and also ASAS-SN Transients page.