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ASAS-SN Discovery of A Probable Supernova in GALEXASC J150551.56-053737.2

ATel #6983; J. M. Fernandez (Observatory Inmaculada del Molino), R. A. Koff (Antelope Hills Observatory), S. Kiyota (Variable Star Observers League in Japan), 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), J. Brimacombe (Coral Towers Observatory), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), E. Conseil (Association Francaise des Observateurs d'Etoiles Variables), B. Nicholls (Mt. Vernon Obs., New Zealand)
on 23 Jan 2015; 19:58 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 #: 6988

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the double 14-cm "Cassius" telescope in Cerro Tololo, Chile, we discovered a new transient source, most likely a supernova, in the galaxy GALEXASC J150551.56-053737.2:

Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag 
ASASSN-15bm  15:05:51.58   -05:37:37.05      2015-01-22.36    16.9 

ASASSN-15bm was discovered in images obtained on UT 2015-01-22.36 at V~16.9 mag. We also detect the object in images obtained on UT 2015-01-23.35 (V~16.7) and UT 2015-01-21.60 (V~17.1). We do not detect (V>17.4) the object in images taken on UT 2015-01-19.61 and before. Images obtained by J. M. Fernandez on UT 2015-01-23.27 with a 20-cm Celestron C8 telescope at Observatory Inmaculada del Molina in Osuna, Spain, by R. A. Koff on UT 2015-01-23.48 using a Meade LX-200 25-cm telescope located at Antelope Hills Observatory, and by S. Kiyota on UT 2015-01-23.57 using a Planewave CDK 0.61-m telescope located at Sierra Remote Observatory confirm 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-15bm is approximately 0.1" North and 0.1" East from the center of the galaxy GALEXASC J150551.56-053737.2, an edge-on galaxy with no redshift available 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.