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ASAS-SN Discovery of A Probable Supernova in AM 1255-315

ATel #7604; B. Nicholls (Mt. Vernon Obs., New Zealand), J. Brimacombe (Coral Towers Observatory), S. Kiyota (Variable Star Observers League in Japan), T. W.-S. Holoien, 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), D. Bersier (LJMU), Subo Dong (KIAA-PKU), E. Falco (CfA), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), E. Conseil (Association Francaise des Observateurs d'Etoiles Variables), G. Krannich (Roof Observatory Kaufering), G. Masi (Virtual Telescope Project, Ceccano, Italy)
on 8 Jun 2015; 16:50 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 #: 7605

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 AM 1255-315.

ASASSN-15kp was discovered in images obtained on UT 2015-06-07.99 at V~16.0 mag. We also detect the object in images obtained on UT 2015-06-07.17 (V~16.2). We do not detect (V>16.1) the object in images taken on UT 2015-06-07.16 and before. Images obtained by B. Nicholls on UT 2015-06-08.25 the 30cm telescope at Mt. Vernon Observatory, by J. Brimacombe on UT 2015-06-08.46 with the CDK 43-cm telescope at Savannah Skies Observatory,and by S. Kiyota on UT 2015-06-08.52 using a 0.5m CDK + FLI PL-9000 at the ITelescope.NET site at Siding Springs Observatory confirm the discovery of the transient. This figure shows the archival DSS image of the host (left) and the B. Nicholls confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the B. Nicholls image.

The position of ASASSN-15kp is approximately 7.8" South and 2.0" West from the center of the galaxy AM 1255-315 (z=0.017402, d=76.7 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.7 (m-M=34.42, A_V=0.23). 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-15kp  12:58:41.76   -32:07:25.99      2015-06-07.99      16.0          -18.7               8.05 
Obs. UT Date         V mag 
2015-06-07.16        >16.1 
2015-06-07.17         16.2 
2015-06-07.99         16.0 

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.