ASAS-SN Discovery of A Possible Intra-cluster Supernova in Abell S753

ATel #7540; 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, N. Goss, 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), J. Brimacombe (Coral Towers Observatory), E. Falco (CfA), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory)
on 20 May 2015; 19:22 UT
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

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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, possibly a supernova, in the galaxy cluster Abell S753.

ASASSN-15jo was discovered in images obtained on UT 2015-05-20.14 at V~16.4 mag. We do not detect (V>17.5) the object in images taken on UT 2015-05-16.13 and before. An image obtained on UT 2015-05-20.71 with the LCOGT 1-m robotic telescope in Sutherland, South Africa confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the LCOGT g-band confirmation image (right). The red circle has a radius of 3" and is centered on the position of the transient in the LCOGT image.

The position of ASASSN-15jo is roughly 2.5' from the center of the galaxy cluster Abell S753, and is approximately 0.9' North and 1.3' East from the center of 2MASX J14063846-3428135, the nearest known galaxy, which does not have a redshift available in NED. The cluster redshift is approximately z=0.013, and if the transient were at this redshift it would have an absolute V-band magnitude of approximately -17.5 (m-M=33.76, A_V=0.176). 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-15jo  14:06:44.67   -34:27:17.44      2015-05-20.14      16.4          N/A               95.64 

 
Obs. UT Date         V mag 
2015-05-16.13        >17.5 
2015-05-20.14         16.4 

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.