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ASAS-SN Discovery of A Probable Supernova in PGC 042600

ATel #7602; J. Brimacombe (Coral Towers Observatory), G. Masi (Virtual Telescope Project, Ceccano, Italy), 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), S. Kiyota (Variable Star Observers League in Japan), G. Krannich (Roof Observatory Kaufering), B. Nicholls (Mt. Vernon Obs., New Zealand)
on 7 Jun 2015; 20:38 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 #: 7610, 7613

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 PGC 042600.

ASASSN-15kn was discovered in images obtained on UT 2015-06-07.09 at V~16.4 mag. We also detect the object in images obtained at the same time with a different ASAS-SN camera. We do not detect (V>16.0) the object in images taken on UT 2015-06-05.16 and before. Images obtained by J. Brimacombe on UT 2015-06-07.64 with the CDK 43-cm telescope at Savannah Skies Observatory and by G. Masi on UT 2015-06-07.83 using the Virtual Telescope Project 17-inch Planewave telescope at Ceccano, Italy confirm the discovery of the transient. This figure shows the archival DSS image of the host (left) and the J. Brimacombe confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the J. Brimacombe image.

The position of ASASSN-15kn is approximately 2.3" South and 3.8" West from the center of the galaxy PGC 042600 (z=0.024734, d=108 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.9 (m-M=35.18, A_V=0.082). 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-15kn  12:41:50.55   -07:10:11.91      2015-06-07.09      16.4          -18.9               4.44 
Obs. UT Date         V mag 
2015-06-05.16        >16.0 
2015-06-07.09         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.