ASASSN-16eu: Discovery of A Probable Supernova in NGC 2649

ATel #9011; T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, 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)
on 30 Apr 2016; 15:17 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@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 NGC 2649.

ASASSN-16eu (AT 2016ccf) was discovered in images obtained on UT 2016-04-30.210 at V~17.1 mag. We also detect the object in images obtained on UT 2016-04-27.26 (V~17.4). We do not detect (V>17.6) the object in images taken on UT 2016-04-25.31 and before. This figure shows the archival DSS image (left), the ASAS-SN V-band reference image (middle-left), the ASAS-SN 2016-04-30 V-band discovery image (middle-right), and the ASAS-SN 2016-04-30 V-band subtraction image (right). The red circle has a radius of 10" and is centered on the position of the transient in the ASAS-SN data.

The position of ASASSN-16eu is approximately 6.3" South and 34.3" East from the center of the galaxy NGC 2649 (z=0.014126, d=61.7 Mpc, via NED), giving an absolute V-band magnitude of approximately -16.9 (m-M=33.95, A_V=0.086). 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-16eu  08:44:11.05    +34:42:55.8      2016-04-30.210      17.1          -16.9               34.87 

 
Obs. UT Date         V mag 
2016-04-25.31        >17.6 
2016-04-27.26         17.4 
2016-04-30.21         17.1 

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.