ASASSN-16gm: Discovery of A Probable Supernova in GALEXASC J200348.67-601528.7

ATel #9188; J. Brimacombe (Coral Towers Observatory), J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, 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), B. Nicholls (Mt. Vernon Obs., New Zealand), R. S. Post (Post Astronomy), G. Stone (Sierra Remote Observatories), W. Wiethoff (University of Minnesota, Duluth)
on 24 Jun 2016; 16:23 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 "Cassius" telescope in Cerro Tololo, Chile, we discovered a new transient source, most likely a supernova, in the galaxy GALEXASC J200348.67-601528.7.

ASASSN-16gm (AT 2016cyh) was discovered in images obtained on UT 2016-06-24.31 at V~16.5 mag. We do not detect (V>16.8) the object in images taken on UT 2016-06-21.16 and before. An image obtained on 2016-06-24 by J. Brimacombe confirms the discovery 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-16gm is approximately 8.3" North and 4.1" East from the center of the galaxy GALEXASC J200348.67-601528.7 (no redshift information available from 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-16gm  20:03:49.229   -60:15:20.36     2016-06-24.31      16.5             N/A               9.26 

 
Obs. UT Date         V mag 
2016-06-21.16        >16.8 
2016-06-24.31         16.5 

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 Mt. Cuba Astronomical Foundation, George Skestos, 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.