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ASAS-SN Discovery of A Probable Supernova in 2MASX J13080914+2749354

ATel #7551; J. Brimacombe (Coral Towers Observatory), T. W.-S. Holoien (Ohio State), D. Bersier (LJMU), K. Z. Stanek, C. S. Kochanek, J. S. Brown, 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), Subo Dong (KIAA-PKU), E. Falco (CfA), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), J. M. Fernandez (Observatory Inmaculada del Molino), S. Kiyota (Variable Star Observers League in Japan), B. Nicholls (Mt. Vernon Obs., New Zealand), J. Nicolas (Groupe SNAUDE, France), W. Wiethoff (University of Minnesota, Duluth)
on 22 May 2015; 16:00 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

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 J13080914+2749354.

ASASSN-15jt was discovered in images obtained on UT 2015-05-22.34 at V~17.1 mag. We also marginally detect the object in images obtained on UT 2015-05-21.37 (V~17.4). We do not detect (V>17.5) the object in images taken on UT 2015-05-20.31 and before. An image obtained by J. Brimacombe on UT 2015-05-22.57 with the CDK 43-cm telescope at Savannah Skies Observatory confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the J. Brimacombe 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-15jt is approximately 0.9" South and 0.3" East from the center of the galaxy 2MASX J13080914+2749354 (z=0.022999, d=99.9 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.9 (m-M=35.00, A_V=0.031). 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-15jt  13:08:09.13   +27:49:34.91      2015-05-22.34      17.1          -17.9               0.95 
Obs. UT Date         V mag 
2015-05-20.31        >17.5 
2015-05-21.37         17.4 
2015-05-22.34         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.