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ASAS-SN Discovery of A Probable Supernova in 2MASX J15322270+4150586

ATel #7780; G. Masi (Virtual Telescope Project, Ceccano, Italy), J. Nicolas (Groupe SNAUDE, France), J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, A. B. Danilet, G. Simonian, U. Basu, 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), J. Brimacombe (Coral Towers Observatory), E. Falco (CfA), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory)
on 9 Jul 2015; 23:16 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 7787

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 J15322270+4150586.

ASASSN-15mg was discovered in images obtained on UT 2015-07-09.37 at V~17.1 mag. We do not detect (V>17.3) the object in images taken on UT 2015-07-06.38 and before. An image obtained on 2015-07-09 by G. Masi confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the G. Masi confirmation image (right). The red circle has a radius of 3" and is centered on the position of the transient in the G. Masi image.

The position of ASASSN-15mg is approximately 1.29" North and 0.54" West from the center of the galaxy 2MASX J15322270+4150586 (z=0.043, d=183 Mpc, via NED), giving an absolute V-band magnitude of approximately -19.3 (m-M=36.31, A_V=0.089). Properties of the new source 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-15mg  15:32:22.80    +41:50:59.6      2015-07-09.37      17.1          -19.3               1.4 
Obs. UT Date         V mag 
2015-07-06.38        >17.3 
2015-07-09.37         17.1 

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.