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ASAS-SN Discovery of A Probable Supernova in SDSS J100807.76+191758.2

ATel #8157; J. Brimacombe (Coral Towers Observatory), R. A. Koff (Antelope Hills Observatory), S. Kiyota (Variable Star Observers League in Japan), J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, D. Godoy Rivera (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, Ping Chen (KIAA-PKU), G. Krannich (Roof Observatory Kaufering), B. Nicholls (Mt. Vernon Obs., New Zealand), J. Nicolas (Groupe SNAUDE, France)
on 13 Oct 2015; 13:45 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Jonathan Brown (brown@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 8297

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 SDSS J100807.76+191758.2.

ASASSN-15rb was discovered in images obtained on UT 2015-10-12.62 at V~16.7 mag. We do not detect (V>16.9) the object in images taken on UT 2015-05-29.26 and before. An image obtained on 2015-10-13 by J. Brimacombe confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the J. Brimacombe confirmation image (right). The red circle has a radius of 3" and is centered on the position of the transient in the J. Brimacombe image.

The position of ASASSN-15rb is approximately 1.08" North and 7.05" East from the center of the galaxy SDSS J100807.76+191758.2 (z=0.033574, d=146 Mpc, via NED), giving an absolute V-band magnitude of approximately -19.2 (m-M=35.82, A_V=0.071). 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-15rb  10:08:08.24    +19:17:59.38      2015-10-12.62      16.7          -19.2               7.13 
Obs. UT Date         V mag 
2015-05-29.26        >16.9 
2015-10-12.62         16.7 

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 Science Fund. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.