ASASSN-16ej: Discovery of A Probable Supernova in UGC 11409

ATel #8939; S. Kiyota (Variable Star Observers League in Japan), R. A. Koff (Antelope Hills 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), J. Brimacombe (Coral Towers Observatory), G. Bock (Runaway Bay Observatory, Australia), E. Conseil (Association Francaise des Observateurs d'Etoiles Variables), J. M. Fernandez (Observatory Inmaculada del Molino), G. Masi (Virtual Telescope Project, Ceccano, Italy)
on 12 Apr 2016; 21:09 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 UGC 11409.

ASASSN-16ej (AT 2016bmc) was discovered in images obtained on UT 2016-04-11.56 at V~16.9 mag. We also detect the object in images obtained on UT 2016-04-10.50 (V~17.0) and UT 2016-04-04.62 (V~17.4). We do not detect (V>16.8) the object in images taken on UT 2016-04-03.61 and before. Images obtained on 2016-04-12 by S. Kiyota and R. Koff confirm the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the S. Kiyota confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the S. Kiyota image.

The position of ASASSN-16ej is approximately 0.7" South and 0.8" West from the center of the galaxy UGC 11409 (z=0.028016, d=115 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.8 (m-M=35.25, A_V=0.477). 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-16ej  19:10:37.327  +37:39:17.02      2016-04-11.56      16.9          -18.8               1.06 

 
Obs. UT Date         V mag 
2016-04-03.61        >16.8 
2016-04-04.62         17.4 
2016-04-10.50         17.0 
2016-04-11.56         16.9 

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.