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ASAS-SN Discovery of A Probable Bright Supernova in HIPASS J1919-33

ATel #7989; J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, G. Simonian, U. Basu, D. Godoy, J. F. Beacom, T. A. Thompson (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong (KIAA-PKU), J. Brimacombe (Coral Towers Observatory)
on 3 Sep 2015; 16:46 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 #: 7990, 7997

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 HIPASS J1919-33.

ASASSN-15oz was discovered in images obtained on UT 2015-08-31.09 at V~14.6 mag. We also detect the object in images obtained on UT 2015-09-03.08 (V~14.5). We do not detect (V>17.8) the object in images taken on UT 2015-08-23.06 and before. This figure shows the archival DSS image (left), the ASAS-SN prediscovery image (center), and the ASAS-SN discovery image (right). The red circle has a radius of 5" and is centered on the position of the transient in the discovery image.

The position of ASASSN-15oz is approximately 1" North and 10.35" West from the center of the galaxy HIPASS J1919-33 (z=0.006929, d=30 Mpc, via SIMBAD), giving an absolute V-band magnitude of approximately -17.7 (m-M=32.4, A_V=0.253). 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-15oz  19:19:33.49    -33:46:02      2015-08-31.09      14.6          -17.8               10.4 
Obs. UT Date         V mag 
2015-08-23.06        >17.8 
2015-08-31.09         14.6 
2015-09-03.08         14.5 

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 and by the Mt. Cuba Astronomical Foundation. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.