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ASAS-SN Discovery of A Probable Supernova in UGC 04251

ATel #8496; 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), G. Bock (Runaway Bay Observatory, Australia), E. Conseil (Association Francaise des Observateurs d'Etoiles Variables), I. Cruz (Cruz Observatory), S. Kiyota (Variable Star Observers League in Japan), G. Masi (Virtual Telescope Project, Ceccano, Italy), L. A.G. Monard (Klein Karoo Observatory), W. Wiethoff (University of Minnesota, Duluth)
on 2 Jan 2016; 23:03 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Jonathan Brown (brown@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

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 04251.

ASASSN-16aa (AT 2016a) was discovered in images obtained on UT 2016-01-02.42 at V~16.8 mag. We also detect the object in images taken on UT 2015-12-31.48 (V~16.6). We do not detect (V>17.4) the object in images taken on UT 2015-12-30.50 and before. An image obtained on 2016-01-02 with the LCOGT 1-m robotic telescope at SAAO confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the LCOGT confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the LCOGT image.

The position of ASASSN-16aa is approximately 6.8" South and 4.2" West from the center of the galaxy UGC 04251 (z=0.017375, d=76 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.7 (m-M=34.36, A_V=0.124). 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-16aa  08:09:14.550  +00:16:50.61      2016-01-02.42      16.8          -17.7               7.99 
Obs. UT Date         V mag 
2015-12-30.50        >16.9       
2015-12-31.48         16.6       
2016-01-02.42         16.8        

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.