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ASAS-SN Discovery of A Probable Supernova in ESO 536-G008

ATel #7522; J. Brimacombe (Coral Towers 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)
on 17 May 2015; 19:57 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

Subjects: Optical, Supernovae, Transient

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the double 14-cm "Cassius" telescope in Cerro Tololo, Chile, we discovered a new transient source, most likely a supernova, in the galaxy ESO 536-G008.

ASASSN-15ji was discovered in images obtained on UT 2015-05-17.38 at V=17.2, and it was not detected in images obtained on UT 2015-05-16.37 (V>17.2). An image obtained by J. Brimacombe on UT 2015-05-17T17:20 using a 33-cm telescope at Savannah Skies Observatory, Australia, confirms 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-15ji is approximately 13.5" from the center of the galaxy ESO 536-G008 (z=0.055592, d=233 Mpc, via NED), giving an absolute V-band magnitude of approximately -19.7 (m-M=36.84, A_V=0.08). 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-15ji  23:35:14.358   -22:44:24.08   2015-05-17.38     17.2         -19.7                 13.5 
ASASSN-15ji (assuming it is confirmed via spectroscopy) is the highest redshift supernova discovered by ASAS-SN to date,

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.