ASASSN-16ff: Discovery of A Probable Supernova in ESO 218-G008

ATel #9058; J. Brimacombe (Coral Towers Observatory), S. Kiyota (Variable Star Observers League in Japan), J. S. Brown, T. W.-S. Holoien, K. Z. Stanek, 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), R. A. Koff (Antelope Hills Observatory), L. A.G. Monard (Klein Karoo Observatory)
on 16 May 2016; 19:49 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 ESO 218-G008.

ASASSN-16ff (AT 2016cdd) was discovered in images obtained on UT 2016-05-14.15 at V~16.1 mag. We also detect the object in images obtained on UT 2016-05-15.11 (V~16.2). We do not detect (V>17.4) the object in images taken on UT 2016-04-08.27 and before. An image obtained on 2016-05-16 by S. Kiyota confirms the discovery of the transient. This figure shows the archival DSS 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-16ff is approximately 1.1" North and 0.4" West from the center of the galaxy ESO 218-G008 (z=0.008731, d=39.6 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.4 (m-M=32.97, A_V=0.506). 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-16ff  12:31:53.636   -51:44:50.83     2016-05-14.15      16.1          -17.4               1.14 

 
Obs. UT Date         V mag 
2016-04-08.27        >17.4 
2016-05-14.15         16.1 
2016-05-15.11         16.2 

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.