ASASSN-16ai: Discovery of A Probable Supernova in UGC 09450

ATel #8537; J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, 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)
on 13 Jan 2016; 01:52 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Jonathan Brown (brown@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 quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, most likely a supernova, in the galaxy UGC 09450.

ASASSN-16ai was discovered in images obtained on UT 2016-01-12.58 at V~17.0 mag. We also detect the object in images obtained on UT 2016-01-10.57 (V~17.0), UT 2016-01-07.61 (V~17.2), UT 2016-01-03.59 (V~17.1), and UT 2015-12-29.64 (V~17.2). We do not detect (V>16.6) the object in images taken on UT 2015-12-24.62 and before. This figure shows the ASAS-SN V-band reference image (left), the ASAS-SN subtraction image (middle), and the archival SDSS image of the host (right). The red circle has a radius of 5" and is centered on the position of the transient in the subtraction image.

The position of ASASSN-16ai is approximately 4.4" South and 8.6" West from the center of the galaxy UGC 09450 (z=0.014900, d=64.6 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.1 (m-M=34.05, A_V=0.088). 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-16ai  14:39:44.73    +23:23:43.27     2016-01-12.58      17.0          -17.1               9.66 

 
Obs. UT Date         V mag 
2015-12-24.62        >16.6 
2015-12-29.64         17.2 
2016-01-03.59         17.1 
2016-01-07.61         17.2 
2016-01-10.57         17.0 
2016-01-12.58         17.0 

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, George Skestos, 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.