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ASAS-SN Discovery of A Probable Supernova in NGC 5517

ATel #7626; S. Kiyota (Variable Star Observers League in Japan), J. Brimacombe (Coral Towers Observatory), T. W.-S. Holoien, K. Z. Stanek, 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), Subo Dong (KIAA-PKU), E. Falco (CfA), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), E. Conseil (Association Francaise des Observateurs d'Etoiles Variables), G. Masi (Virtual Telescope Project, Ceccano, Italy), B. Nicholls (Mt. Vernon Obs., New Zealand), J. Nicolas (Groupe SNAUDE, France), D. E. Polsgrove, D. J. Della-Rose, S. J. Novotny (Falcon Telescope Network, US Air Force Academy), A. Wilber (ASU), J. Zinn (Ohio State), R. M. Wagner (LBTO/Ohio State), M. Neric (ASU)
on 12 Jun 2015; 18:01 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

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, most likely a supernova, in the galaxy NGC 5517.

ASASSN-15la was discovered in images obtained on UT 2015-06-11.33 at V~16.5 mag. We also detect the object in images obtained on UT 2015-06-07.210 (V~17.2). We do not detect (V>16.9) the object in images taken on UT 2015-06-06.44 and before. Images obtained by S. Kiyota on UT 2015-06-12.14 using a Planewave CDK 0.43-m telescope located near Mayhill, New Mexico and by J. Brimacombe on UT 2015-06-12.19 with the RCOS 51-cm telescope in New Mexico confirm the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the S. Kiyota confirmation image (right). The red circle has a radius of 2" and is centered on the position of the transient in the S. Kiyota image.

The position of ASASSN-15la is approximately 0.6" North and 0.3" West from the center of the galaxy NGC 5517 (z=0.027903, d=120 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.9 (m-M=35.39, A_V=0.052). 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-15la  14:12:51.22   +35:42:39.85      2015-06-11.33      16.5          -18.9               0.67 
Obs. UT Date         V mag 
2015-06-06.44        >16.9 
2015-06-07.21         17.2 
2015-06-11.33         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.