ASASSN-16hw: Discovery of A Probable Supernova in GALEXASC J215327.92-342420.8

ATel #9278; J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, J. Shields, 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, S. Bose, Ping Chen (KIAA-PKU), J. Brimacombe (Coral Towers Observatory)
on 29 Jul 2016; 18:07 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 J215327.92-342420.8.

ASASSN-16hw (AT 2016ekt) was discovered in images obtained on UT 2016-07-29.34 at V~14.9 mag. We also detect the object in images obtained on UT 2016-07-26.35 (V~15.1) and UT 2016-07-24.27 (V~15.4). We do not detect (V>16.4) the object in images taken on UT 2016-07-17.13 and before. This figure shows the archival DSS image of the host (left) and the the ASAS-SN reference image (middle) and the ASAS-SN subtraction image (right). The red circle has a radius of 10" and is centered on the position of the transient in the subtraction image.

The position of ASASSN-16hw is approximately 0.7" North and 1.1" West from the center of the galaxy GALEXASC J215327.92-342420.8 (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-16hw  21:53:27.882   -34:24:20.95     2016-07-29.34      14.9            N/A                 1.3 

 
Obs. UT Date         V mag 
2016-07-17.13        >16.4 
2016-07-24.27         15.4 
2016-07-26.35         15.1 
2016-07-29.34         14.9 

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.