ASAS-SN Discovery of a Very Bright Optical Transient

ATel #7850; Subo Dong, Ping Chen (KIAA-PKU), K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, J. S. Brown, A. B. Danilet, G. Simonian, U. Basu, J. F. Beacom, T. A. Thompson (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), J. Brimacombe (Coral Towers Observatory), E. Falco (CfA), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory)
on 28 Jul 2015; 17:05 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Subo Dong (dongsubo@pku.edu.cn)

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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:

Object       RA (J2000)   DEC (J2000)     Disc. UT Date     Disc. V mag 
ASASSN-15ni  18:39:58.064  +22:21:17.80    2015-07-28.40     12.9 

ASASSN-15ni was discovered in images obtained on UT 2015-07-28.40 at V~12.9 mag. We do not detect (V>17.3) the object in images taken on UT 2015-07-24.42 and before. Images obtained by LCOGT 1.0m A in Dome A at Siding Spring on UT 2015-07-28.58 confirm the discovery of the transient. This figure shows the archival DSS images in red (left) and blue (middle) and the LCOGT V-band confirmation image (right). The red circle has a radius of 3" and is centered on the position of the transient in the LCOGT image. There is no known source within 4" in any catalogs listed in VizieR Service. There appears to be a faint source at the position of the transient in archival DSS blue image.

The nature of the optical transient is unknown. Follow-up observations, especially spectroscopic, are encouraged.

We thank LCOGT and its staff for their continued support of ASAS-SN. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.