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ASASSN-16oq: Discovery of A Probable Supernova in AM 1228-353 NED02

ATel #9838; T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, J. Shields (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, S. Bose, Ping Chen (KIAA-PKU), J. Brimacombe (Coral Towers Observatory)
on 8 Dec 2016; 20:02 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 9850

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 galaxy AM 1228-353 NED02.

ASASSN-16oq (AT 2016ito) was discovered in images obtained on UT 2016-12-08.36 at V~15.4 mag. We also detect the object in images obtained on UT 2016-12-06.36 (V~15.9) and UT 2016-12-01.35 (V~15.5). We do not detect (V>16.4) the object in images taken on UT 2016-08-20.97 and before. (The field containing this transient only recently became observable from behind the Sun, which is why there is a gap in our observations.) This figure shows the archival DSS image of the host (left), the ASAS-SN V-band reference image of the host (center), and the 2016-12-08 ASAS-SN V-band subtraction image of the transient (right). The red circle has a radius of 5" and is centered on the position of the transient in the ASAS-SN image.

The position of ASASSN-16oq is approximately 2.7" South and 10.1" West from the center of the galaxy AM 1228-353 NED02 (z=0.019920, d=87.4 Mpc, via NED), giving an absolute V-band magnitude of approximately -19.5 (m-M=34.71, A_V=0.168). 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-16oq  12:31:09.000   -35:55:49.76     2016-12-08.36      15.4          -19.5               10.45 
 
Obs. UT Date         V mag 
2016-08-20.97        >16.4 
2016-12-01.35         15.5 
2016-12-06.36         15.9 
2016-12-08.36         15.4 

Follow-up observations are encouraged.

While we are participating in the TNS system to minimize potential confusion, ASAS-SN will continue using ASASSN-16xx transient names as our primary nomenclature (including supernovae, but also other classes of transients), and we encourage others to do the same. We prefer merging the names as ASASSN-16xx (AT2016xyz) to preserve, rather than anonymize, the origin of the transient.

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 Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and 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.