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ASAS-SN Discovery of A Probable Supernova in NGC 5996

ATel #7078; T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, A. B. Danilet, G. Simonian, U. Basu, N. Goss, J. F. Beacom (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong (KIAA-PKU), P. R. Wozniak (LANL), E. Falco (CfA), J. Brimacombe (Coral Towers Observatory), D. Szczygiel, G. Pojmanski (Warsaw University Observatory)
on 15 Feb 2015; 17:44 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 7086, 7087

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 5996:

Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag 
ASASSN-15db  15:46:58.69   +17:53:02.55      2015-02-15.58    15.2 

ASASSN-15db was discovered in images obtained on UT 2015-02-15.58 at V~15.2 mag. We also detect the object in images obtained on UT 2015-02-08.55 (V~16.7). We do not detect (V>17.0) the object in images taken on UT 2015-02-07.59 and before. An image obtained on UT 2015-02-15.70 with the LCOGT 1-m robotic telescope at Siding Springs Observatory confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the LCOGT confirmation image (right). The red lines indicate the position of the transient in the LCOGT image.

The position of ASASSN-15db is approximately 0.5" South and 2.8" West from the center of the galaxy NGC 5996 (z=0.010998, d=47.1 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.3 (m-M=33.37, A_V=0.093). Follow-up observations are encouraged.

We thank LCOGT and its staff for their continued support of ASAS-SN. ASAS-SN is supported in part by Mt. Cuba Astronomical Foundation. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.