ASAS-SN Discovery of A Probable Supernova in 2MASX J11200680+3407396

ATel #7507; J. M. Fernandez (Observatory Inmaculada del Molino), J. Brimacombe (Coral Towers Observatory), R. A. Koff (Antelope Hills Observatory), K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, J. S. Brown, A. B. Danilet, G. Simonian, U. Basu, N. Goss, J. F. Beacom, T. A. Thompson (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong (KIAA-PKU), E. Falco (CfA), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), S. Kiyota (Variable Star Observers League in Japan), B. Nicholls (Mt. Vernon Obs., New Zealand)
on 14 May 2015; 15:53 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"), 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 2MASX J11200680+3407396.

ASASSN-15jb was discovered in images obtained on UT 2015-05-13.37 at V=17.2 mag. It was also marginally detected in images taken on 2015-05-08.29 at V=17.6. It was not detected (V>17.1) on UT 2015-05-06.38 and before. Images obtained by J. M. Fernandez, J. Brimacombe and R. A. Koff on UT 2015-05-14, using several different telescopes, confirm the discovery of the transient. This figure shows the archival DSS image of the host (left) and the confirmation image (right). The red circle has a radius of 3" and is centered on the position of the transient in the J. Brimacombe image.

The position of ASASSN-15jb is approximately 6" from the center of the galaxy 2MASX J11200680+3407396 (z=0.035661, d=155 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.8 (m-M=35.95, A_V=0.07). Properties of the new sources and photometry are summarized in the tables below:

 
Object       RA (J2000)     DEC (J2000)    Disc. UT Date   Disc. V mag  Approx. Abs. Mag   Offset from Host (") 
ASASSN-15jb  11:20:06.399  +34:07:43.00    2015-05-13.37      17.2        -18.8                 6.0  

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.