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ASAS-SN Discovery of A Probable Supernova in GALEXASC J202933.17-615703.5

ATel #8313; 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), J. Brimacombe (Coral Towers Observatory)
on 20 Nov 2015; 18:58 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 GALEXASC J202933.17-615703.5.

ASASSN-15ta was discovered in images obtained on UT 2015-11-14.09 at V~16.8 mag. We also detect the object in images obtained on UT 2015-11-20.08 (V~16.0). We do not detect (V>17.5) the object in images taken on UT 2015-11-12.11 and before. This figure shows the archival DSS image of the host (left), the ASAS-SN V-band reference image of the host (center), and the 2015-11-20 ASAS-SN subtraction image (right). The red circle has a radius of 3" and is centered on the ASAS-SN position of the transient.

The position of ASASSN-15ta is approximately 0.1" North and 1.0" West from the center of the UV source GALEXASC J202933.17-615703.5, which has no redshift available in NED. 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-15ta  20:29:33.03    -61:57:03.42      2015-11-14.09      16.8          N/A               1.0 
Obs. UT Date         V mag 
2015-11-12.11        >17.5 
2015-11-14.09         16.8 
2015-11-20.08         16.0 

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.