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ASAS-SN Discovery of A Possible Supernova in an Unknown Host

ATel #7348; 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 6 Apr 2015; 19:46 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 #: 7354

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 an unknown host galaxy:

Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag 
ASASSN-15fy  19:50:22.34    -14:17:45.97     2015-03-29.38    16.9 

ASASSN-15fy was discovered in images obtained on UT 2015-03-29.38 at V~16.9 mag. The transient was originally announced as a cataclysmic variable candidate on our transients page, and we also detect the object in images obtained on UT 2015-03-13.38 (V~16.4), UT 2015-03-19.37 (V~16.5), UT 2015-03-27.35 (V~17), and UT 2015-03-29.38 (V~16.9). We do not detect (V>16.5) the object in images taken on UT 2015-03-08.40 and before. An image obtained on UT 2015-04-05.31 with the LCOGT 1-m robotic telescope at Cerro Tololo, Chile confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the LCOGT confirmation image (right). The red circle has a radius of 2.0" and is centered on the position of the transient in the LCOGT image.

The position of ASASSN-15fy is approximately 3" Southwest from the center of what appears to be an unknown galaxy in the DSS image. Due to the continued slow decline (Delta_V~0.5 mag in nearly a month), we now believe this may be a supernova, possibly superluminous, rather than a CV. 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.