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ASAS-SN Discovery of A Probable Supernova near 2MASXi J0638012-373927

ATel #8383; Subo Dong (KIAA-PKU), C. S. Kochanek, K. Z. Stanek, J. S. Brown, T. W.-S. Holoien, D. Godoy-Rivera, U. Basu (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Ping Chen (KIAA-PKU), J. Brimacombe (Coral Towers Observatory), I. Cruz (Cruz Observatory), S. Kiyota (Variable Star Observers League in Japan)
on 8 Dec 2015; 05:55 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Subo Dong (dongsubo@pku.edu.cn)

Subjects: 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, near the galaxy 2MASXi J0638012-373927.

ASASSN-15tt was discovered in images obtained on UT 2015-12-08.11 at V~17.1 mag. We also detect the object in images obtained on UT 2015-12-06.26 (V~17.0). We do not detect (V>17.5) the object in images taken on UT 2015-12-04.13 and before. A V-band image obtained by 1.0m LCOGT telescope at Cerro Tololo on UT 2015-12-08.21 confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the LCOGT confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the LCOGT image.

The position of ASASSN-15tt is approximately 4" from the center of the galaxy 2MASXi J0638012-373927 (unknown redshift via 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    Offset from Host (") 
ASASSN-15tt  06:38:01.49    -37:39:30.94      2015-12-08.11      17.1                        4 
Obs. UT Date         V mag 
2015-12-04.13        >17.5 
2015-12-06.26         17.0 
2015-12-08.11         17.1 

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.