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ASAS-SN Discovery of A Probable Supernova in 2MASX J22340166-3223490

ATel #8386; B. Nicholls (Mt. Vernon Obs., New Zealand), G. Bock (Runaway Bay Observatory, Australia), J. Brimacombe (Coral Towers Observatory), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, 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), I. Cruz (Cruz Observatory), S. Kiyota (Variable Star Observers League in Japan), G. Krannich (Roof Observatory Kaufering), G. Masi (Virtual Telescope Project, Ceccano, Italy), W. Wiethoff (University of Minnesota, Duluth)
on 8 Dec 2015; 18:07 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@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 galaxy 2MASX J22340166-3223490.

ASASSN-15tu was discovered in images obtained on UT 2015-12-08.09 at V~16.3 mag. We also detect the object in images obtained on UT 2015-12-04.11 (V~16.3). We do not detect (V>17.1) the object in images taken on UT 2015-11-28.02 and before. Images obtained by multiple observers on UT 2015-12-08 confirm the detecttion of the transient. This figure shows the archival DSS image of the host (left) and the J. Brimacombe confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the J. Brimacombe. image.

The position of ASASSN-15tu is approximately 4.4" South and 11.7" East from the center of the galaxy 2MASX J22340166-3223490 (z=0.01260, d=48.3 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.2 (m-M=33.42, A_V=0.038). 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-15tu  22:34:02.58    -32:23:53.58      2015-12-08.09      16.3          -17.2               12.5 
Obs. UT Date         V mag 
2015-11-28.02        >17.1 
2015-12-04.11         16.3 
2015-12-08.09         16.3 

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.