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ASAS-SN Discovery of A Probable Bright Supernova in NGC 4866

ATel #7317; J. Brimacombe (Coral Towers Observatory), K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, 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), D. Bersier (LJMU), Subo Dong (KIAA-PKU), E. Falco (CfA), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), S. Kiyota (Variable Star Observers League in Japan), G. Krannich (Roof Observatory Kaufering), B. Nicholls (Mt. Vernon Obs., New Zealand)
on 30 Mar 2015; 19:19 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

Subjects: Optical, Supernovae

Referred to by ATel #: 7333

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new bright, transient source, most likely a supernova, in the galaxy NGC 4866

Object       RA (J2000)     DEC (J2000)    Disc. UT Date   Disc. V mag  
ASASSN-15ga  12:59:27.292  +14:10:15.79    2015-03-30.29    15.6 
ASASSN-15ga was discovered in images obtained on UT 2015-03-30.29 at V~15.6 mag. We also detect the object in images obtained on UT 2015-03-28.51 (V=16.6) and 2015-03-29.29 (V=16.4), and there is also a nominal detection on UT 2015-03-27.36, which needs to be further investigated (the flux of the supernova is only few percent of the flux of the host galaxy at this location). We do not detect (V>17.5) the object in images taken on UT 2015-03-24.45 and before. Follow-up image obtained by J. Brimacombe confirms the discovery of the transient. This figure shows the archival SDSS image of the host (left) and the J. Brimacombe confirmation image (right). The red circle has a radius of 2" and is centered on the position of the transient in the confirmation image, obtained on UT 2015-03-30.72 with 33-cm RCOS telescope at the Savannah Skies Observatory.

The position of ASASSN-15ga is approximately 2.4" from the center of the galaxy NGC 4866 (z=0.006631, d=31.6 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.0 (m-M=32.5, A_V=0.08). 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.