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ASAS-SN Discovery of A Bright Transient Near 2MASX J19381271-7925320

ATel #7461; B. Nicholls (Mt. Vernon Obs., New Zealand), 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), J. M. Fernandez (Observatory Inmaculada del Molino), S. Kiyota (Variable Star Observers League in Japan), R. A. Koff (Antelope Hills Observatory), G. Krannich (Roof Observatory Kaufering), L. A.G. Monard (Klein Karoo Observatory), J. Nicolas (Groupe SNAUDE, France), W. Wiethoff (University of Minnesota, Duluth)
on 30 Apr 2015; 16:12 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, possibly a supernova, near the galaxy 2MASX J19381271-7925320.

ASASSN-15id was discovered in images obtained on UT 2015-04-29.28 at V~16.0 mag. We also detect the object in images obtained on UT 2015-04-28.23 (V~16.0). We do not detect (V>17.1) the object in images taken on UT 2015-04-26.34 and before. An image obtained by B. Nicholls on UT 2014-04-30.38 using the 30cm telescope at Mt. Vernon Observatory confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the B. Nicholls confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the B. Nicholls image.

The position of ASASSN-15id is approximately 18.6" South and 44.5" East from the center of the galaxy 2MASX J19381271-7925320, which has no available redshift in NED. The transient is also located approximately 26.7" North and 13.0" West from another irregular source, possibly an uncatalogued galaxy, in archival DSS images. Given the proximity to these two possible hosts and the lack of a known stellar counterpart at these coordinates, ASASSN-15id could be a supernova. However, a cataclysmic variable outburst is also a possible explanation for the transient.

Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag  Approx. Abs. Mag   Offset from Host (") 
ASASSN-15id  19:38:30.11   -79:25:51.93      2015-04-29.28      16.0          N/A                   48.23 
Obs. UT Date         V mag 
2015-04-26.34        >17.1 
2015-04-28.23         16.0 
2015-04-29.28         16.0 

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.