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ASAS-SN Discovery of A Probable Supernova in an Uknown Redshift Host Galaxy

ATel #6984; J. Brimacombe (Coral Towers Observatory), S. Kiyota (Variable Star Observers League in Japan), R. A. Koff (Antelope Hills Observatory), 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), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), E. Conseil (Association Francaise des Observateurs d'Etoiles Variables), J. M. Fernandez (Observatory Inmaculada del Molino), B. Nicholls (Mt. Vernon Obs., New Zealand)
on 24 Jan 2015; 16:43 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

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, near the UV source GALEXASC J155536.57+664316.5:

Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag 
ASASSN-15bn  15:55:35.35    +66:43:19.31      2015-01-23.63    16.7 

ASASSN-15bn was discovered in images obtained on UT 2015-01-23.63 at V~16.7 mag. We do not detect (V>17.2) the object in images taken on UT 2015-01-21.64 and before. Images obtained by J. Brimacombe on UT 2015-01-24.42 with the RCOS 51-cm telescope in New Mexico, by S. Kiyota on UT 2015-01-24.45 using a Planewave CDK 0.61-m telescope located at Sierra Remote Observatory, and by R. A. Koff on UT 2015-01-24.50 using a Meade LX-200 25-cm telescope located at Antelope Hills Observatory confirm the discovery of the transient. This figure shows the archival DSS image of the host (left) and the J. Brimacombe confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the J. Brimacombe image.

The position of ASASSN-15bn is approximately 2.7" North and 7.2" West from the center of GALEXASC J155536.57+664316.5, a UV source that appears to be a dwarf galaxy but is not catalogued as a galaxy in NED. Follow-up observations, particularly spectroscopy, 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.