ASAS-SN Discovery of A Probable Supernova in Mrk 1182
G. Masi (Virtual Telescope Project, Ceccano, Italy), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, D. Godoy-Rivera, U. Basu (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, Ping Chen (KIAA-PKU), J. Brimacombe (Coral Towers Observatory), S. Kiyota (Variable Star Observers League in Japan), G. Krannich (Roof Observatory Kaufering), L. A.G. Monard (Klein Karoo Observatory)
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 transient source, most likely a supernova, in the galaxy Mrk 1182.

ASASSN-15un was discovered in images obtained on UT 2015-12-28.22 at V~17.0 mag. We do not detect (V>16.5) the object in images taken on UT 2015-12-26.33 and before. An image obtained by G. Masi on UT 2015-12-28.71 using the Virtual Telescope Project 17-inch Planewave telescope at Ceccano, Italy confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the G. Masi confirmation image (right). The red circle has a radius of 4" and is centered on the position of the transient in the G. Masi image.

The position of ASASSN-15un is approximately 3.0" North and 0.7" East from the center of the galaxy Mrk 1182 (z=0.0292, d=119 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.6 (m-M=35.39, A_V=0.23). Properties of the new source and photometry are summarized in the tables below:

Follow-up observations are encouraged.

We thank LCOGT and its staff for their continued support of ASAS-SN. ASAS-SN is supported by NSF grant AST-1515927, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Mt. Cuba Astronomical Foundation, and the Robert Martin Ayers Sciences Fund. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.
optical,supernovae,transient