ASASSN-16dm: Discovery of A Probable Supernova in 2MASX J11372059-0454450

ATel #8882; S. Kiyota (Variable Star Observers League in Japan), G. Masi (Virtual Telescope Project, Ceccano, Italy), 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), J. Brimacombe (Coral Towers Observatory)
on 30 Mar 2016; 12:59 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 2MASX J11372059-0454450.

ASASSN-16dm (AT 2016blb) was discovered in images obtained on UT 2016-03-30.29 at V~16.3 mag. We also detect the object in images obtained on UT 2016-03-28.28 (V~16.5). We do not detect (V>16.7) the object in images taken on UT 2016-03-20.44 and before. An image obtained on 2016-03-30 by S. Kiyota confirms 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-16dm is approximately 8.5" North and 1.3" East from the center of the galaxy 2MASX J11372059-0454450 (z=0.018300, d=81.4 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.4 (m-M=34.51, A_V=0.143). 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-16dm  11:37:20.639  -04:54:36.84      2016-03-30.29      16.3          -18.4               8.6 

 
Obs. UT Date         V mag 
2016-03-20.44        >16.7 
2016-03-28.28         16.5 
2016-03-30.29         16.3 

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.