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ASAS-SN Discovery of A Probable Supernova in NGC 3157

ATel #7546; 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 21 May 2015; 15:37 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 7557

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 NGC 3157.

ASASSN-15jp was discovered in images obtained on UT 2015-05-21.08 at V~15.6 mag. We do not detect (V>16.6) the object in images taken on UT 2015-05-19.02 and before. This figure shows the archival DSS image of the host (left), the ASAS-SN V-band reference image of the host (center), and the ASAS-SN V-band discovery image (right). The red circle has a radius of 10" and is centered on the position of the transient in the ASAS-SN image.

The position of ASASSN-15jp is approximately 29.7" South and 43.9" West from the center of the galaxy NGC 3157 (z=0.009477, d=43.8 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.9 (m-M=33.21, A_V=0.275). 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-15jp  10:11:38.99    -31:39:04.04     2015-05-21.08      15.6          -17.9               53.0 
Obs. UT Date         V mag 
2015-05-19.02        >16.6 
2015-05-21.08         15.6 

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.