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ASAS-SN Discovery of A Bright Transient Near ESO 382-G030

ATel #7192; T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, A. B. Danilet, G. Simonian, U. Basu, N. Goss, J. F. Beacom, T. A. Thompson (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 9 Mar 2015; 17:12 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Cataclysmic Variable, Supernovae, Transient

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, likely a supernova or cataclysmic variable star, near the galaxy ESO 382-G030:

Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag 
ASASSN-15ek  13:17:06.35    -37:37:37.5      2015-03-09.21    15.4 

ASASSN-15ek was discovered in images obtained on UT 2015-03-09.210 at V~15.4 mag. We also detect the object in images obtained on UT 2015-03-07.19 (V~15.7). We do not detect (V>16.8) the object in images taken on UT 2015-03-05.23 and before. This figure shows the ASAS-SN V-band reference image (left), the ASAS-SN V-band 2015-03-09.21 subtraction image (center), and the archival DSS image of the possible host (right). The red circle has a radius of 5" and is centered on the position of the transient in the ASAS-SN data.

The position of ASASSN-15ek is approximately 83.0" North and 47.0" East from the center of the galaxy ESO 382-G030 (z=0.0055, d=23.8 Mpc, via Hyperleda), corresponding to a distance of 11 kpc at this redshift. Due to the large offset from the possible host galaxy, a cataclysmic variable outburst cannot be ruled out, but if this is a supernova associated with this host it would have an absolute V-band magnitude of approximately -16.7 (m-M=31.88, A_V=0.172). 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.