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ASAS-SN Discovery of A Probable Supernova in CGCG 078-056

ATel #6979; S. Kiyota (Variable Star Observers League in Japan), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, A. B. Danilet, G. Simonian, U. Basu, N. Goss, J. F. Beacom (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong (KIAA-PKU), P. R. Wozniak (LANL), J. Brimacombe (Coral Towers Observatory), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), E. Conseil (Association Francaise des Observateurs d'Etoiles Variables), J. M. Fernandez (Cielos de Osasuna), R. A. Koff (Antelope Hills Observatory), B. Nicholls (Mt. Vernon Obs., New Zealand)
on 22 Jan 2015; 20:17 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 6988, 7021

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, most likely a supernova, in the galaxy CGCG 078-056:

 
Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag 
ASASSN-15bk  15:44:12.43   +11:16:16.38      2015-01-19.62    17.1 

ASASSN-15bk was discovered in images obtained on UT 2015-01-19.62 at V~17.1 mag. We also detect the object in images obtained on UT 2015-01-21.61 (V~17.2). We do not detect (V>17.6) the object in images taken on UT 2015-01-17.62 and before. An image obtained by S. Kiyota on UT 2015-01-22.76 using a 0.5m CDK + FLI PL-9000 at the ITelescope.NET site at Siding Springs Observatory confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the S. Kiyota confirmation image (right). The red circle has a radius of 3.0" and is centered on the position of the transient in the S. Kiyota image.

The position of ASASSN-15bk is approximately 1.6" North and 6.8" East from the center of the galaxy CGCG 078-056 (z=0.034277, d=146 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.9 (m-M=35.83, A_V=0.13). Follow-up observations are encouraged.

We thank LCOGT and its staff for their continued support of ASAS-SN. ASAS-SN is supported in part by Mt. Cuba Astronomical Foundation. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.