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ASAS-SN Discovery of A Probable Supernova in GALEXASC J095959.71-025322.1

ATel #7483; S. Kiyota (Variable Star Observers League in Japan), J. Brimacombe (Coral Towers Observatory), J. M. Fernandez (Observatory Inmaculada del Molino), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, 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), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), L. A.G. Monard (Klein Karoo Observatory)
on 7 May 2015; 16:18 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 #: 7531

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 J095959.71-025322.1.

ASASSN-15ih was discovered in images obtained on UT 2015-05-06.07 at V~16.5 mag. We also detect the object in images obtained on UT 2015-05-04.09 (V~16.2). We do not detect (V>16.3) the object in images taken on UT 2015-05-03.16 and before. Images obtained by S. Kiyota on UT 2014-05-07.11 using a Planewave CDK 0.43-m telescope located near Mayhill, New Mexico and by J. Brimacombe on UT 2015-04-07.14 with the RCOS 51-cm telescope in New Mexico 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-15ih is approximately 8.3" North and 1.2" West from the center of the galaxy GALEXASC J095959.71-025322.1 (z=0.019827, d=87.7 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.3 (m-M=34.71, A_V=0.127). Properties of the new source and photometry are summarized in the tables below:

Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag  Approx. Abs. Mag   Offset from Host (") 
ASASSN-15ih  09:59:59.57    09:59:59.57       -02:53:16.36      16.5          -18.3               8.39 
Obs. UT Date         V mag 
2015-05-03.16        >16.3 
2015-05-04.09         16.2 
2015-05-06.07         16.5 

Follow-up observations 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.