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ASAS-SN Discovery of A Very Bright Supernova in NGC 7213

ATel #8474; 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 30 Dec 2015; 01:54 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 "Cassius" telescope in Cerro Tololo, Chile, we discovered a new transient source, most likely a supernova, in the nearby galaxy NGC 7213.

ASASSN-15us was discovered in images obtained on UT 2015-12-29.03 at V~14.7 mag. We also detect the object in images obtained on UT 2015-12-25.05 (V~16.1). We do not detect (V>17.1) the object in images taken on UT 2015-12-22.06 and before. This figure shows the ASAS-SN V-band reference image (left), the ASAS-SN discovery image (middle), and the archival DSS image of the host (right). The red circle has a radius of 15" and is centered on the position of the transient in the discovery image.

The position of ASASSN-15us is approximately 117" North and 68" West from the center of the galaxy NGC 7213 (z=0.005839, d=21.2 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.0 (m-M=31.63, 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-15us  22:09:09.641  -47:08:02.48      2015-12-29.03      14.7          -17.0               135.33 
 
Obs. UT Date         V mag 
2015-12-22.06        >17.1 
2015-12-25.05         16.1 
2015-12-29.03         14.7 

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