ASAS-SN Discovery of A Probable Bright Supernova in 2MASX J08401168-0435369

ATel #7574; 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), J. M. Fernandez (Observatory Inmaculada del Molino), B. Nicholls (Mt. Vernon Obs., New Zealand), J. Nicolas (Groupe SNAUDE, France), W. Wiethoff (University of Minnesota, Duluth)
on 28 May 2015; 19:11 UT
Distributed as an Instant Email Notice Supernovae
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, most likely a supernova, in the galaxy 2MASX J08401168-0435369.

ASASSN-15kg was discovered in images obtained on UT 2015-05-27.99 at V~16.0 mag. We do not detect (V>16.7) the object in images taken on UT 2015-05-25.97 and before. Images obtained by J. Brimacombe on UT 2015-05-28.12 with the RCOS 51-cm telescope in New Mexico and by S. Kiyota on UT 2015-05-28.14 using a Planewave CDK 0.43-m telescope located near Mayhill, New Mexico 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 4" and is centered on the position of the transient in the J. Brimacombe image.

The position of ASASSN-15kg is approximately 5.9" North and 4.8" East from the center of the galaxy 2MASX J08401168-0435369 (z=0.014257, d=63.3 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.1 (m-M=34.01, A_V=0.058). 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-15kg  08:40:12.01   -04:35:31.00      2015-05-27.99      16.0          -18.1               7.61 

 
Obs. UT Date         V mag 
2015-05-25.97        >16.7 
2015-05-27.99         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.