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ASASSN-15so: Discovery of A Bright Probable Supernova in NGC 3583

ATel #8256; K. Z. Stanek, C. S. Kochanek, J. S. Brown, T. W.-S. Holoien, 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. Masi (Virtual Telescope Project, Ceccano, Italy), B. Nicholls (Mt. Vernon Obs., New Zealand)
on 8 Nov 2015; 17:07 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

Subjects: Optical, Supernovae

Referred to by ATel #: 8259, 8261

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the quadruple 14-cm "Brutus" telescope in Hawaii, we discovered a new transient source, most likely a supernova, in the galaxy NGC 3583.

ASASSN-15so was discovered in images obtained on UT 2015-11-08.63 at V~15.1 mag. We do not detect (V>17.1) the object in images taken on UT 2015-11-03.64 and before.

The position of ASASSN-15so is approximately 1.5" from the center of a relatively nearby, star-forming galaxy NGC 3583, at z=0.007125, corresponding to a distance modulus of 32.44 (physical distance of 30.8 Mpc; NED). That gives an absolute magnitude of M_V=-15.74 (A_V=0.04).

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-15so  11:14:11.037 +48:19 07.24    2015 11 8.62       15.1           -15.74               1.5 
Obs. UT Date          V mag  
2015-11-03.64         >17.1  
2015-11-08.63          15.1  
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 Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, and the Robert Martin Ayers Sciences Fund.