ASASSN-16mt: Discovery of A Probable Supernova in 2MASX J01004149-0026406

ATel #9714; J. Brimacombe (Coral Towers Observatory), R. S. Post (Post Astronomy), G. Stone (Sierra Remote Observatories), G. Masi (Virtual Telescope Project, Ceccano, Italy), B. J. Shappee, Jennifer Van Saders, Mark Seibert (Carnegie Observatories), S. Bose (KIAA-PKU), J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, J. Shields (Ohio State), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, Ping Chen (KIAA-PKU), R. A. Koff (Antelope Hills Observatory)
on 4 Nov 2016; 21:48 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Jonathan Brown (brown@astronomy.ohio-state.edu)

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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 2MASX J01004149-0026406.

ASASSN-16mt (AT 2016hsx) was discovered in images obtained on UT 2016-11-03.42 at V~17.3 mag. We also detect the transient in images obtained on UT 2016-10-30.24 (V~17.3), UT 2016-10-26.40 (V~17.2), and UT 2016-10-24.45 (V~17.4). We do not detect (V>17.4) the object in images taken on UT 2016-10-19.33 and before. An image obtained on 2016-11-03 by J. Brimacombe confirms the discovery of the transient. This figure shows the archival SDSS g-band 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-16mt is approximately 0.3" South and 0.0" West from the center of the galaxy 2MASX J01004149-0026406 (z=0.043602, d=180 Mpc, via NED), giving an absolute V-band magnitude of approximately -19.0 (m-M=36.19, A_V=0.098). We obtained a spectrum of ASASSN-16mt with WFCCD (range 3600-9200 Angs) mounted on the du Pont 2.5m telescope at Las Campanas Observatory. We used SNID (Blondin & Tonry, 2007, ApJ, 666, 1024) to identify the type, phase and redshift of the SN. The spectrum resembles SN Ia approximately 1 week post maximum, at the redshift of the host. 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-16mt  01:00:41.498   -00:26:40.75     2016-11-03.42      17.3          -19.0               0.3 

 
Obs. UT Date         V mag 
2016-10-19.33        >17.4 
2016-10-24.45         17.4 
2016-10-26.40         17.2 
2016-10-30.24         17.3 
2016-11-03.42         17.3 

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, 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.