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ASAS-SN Discovery of Likely SN in the Starburst Dwarf galaxy SDSS J161633.82-003519.7

ATel #5333; J. L. Prieto (Princeton), K. Z. Stanek, B. J. Shappee, C. S. Kochanek, T. W-S. Holoien, J. Jencson, U. Basu, J. F. Beacom (Ohio State), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), M. Dubberley, M. Elphick, S. Foale, E. Hawkins, D. Mullens, W. Rosing, R. Ross, Z. Walker (Las Cumbres Observatory), J. Brimacombe (Coral Towers Observatory)
on 28 Aug 2013; 13:14 UT
Credential Certification: Jose L. Prieto (jose@obs.carnegiescience.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 5334, 5343

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the double 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, most likely a supernova:

Object        RA (J2000)    DEC (J2000)   Disc. UT Date    Disc. V mag    
ASASSN-13cg   16:16:34.06  -00:35:27.38     Aug. 28.24         16.05 
No source is detected on 08/21 and earlier images (V > 17 mag).

The new source is approx. 7.7" South and 3.6" East of its host galaxy SDSS J161633.82-003519.7 (CGCG 023-030) at z = 0.01646 (d=70 Mpc, mu=34.2 mag), which implies an absolute V mag of -18.5 mag (A_V=0.33 mag, Schlafly & Finkbeiner 2011) for the SN located at a projected distance of ~3 kpc from its host. The host galaxy shows strong nebular emission lines characteristic of a starburst and its absolute magnitudes (Mg= -18.6, Mr= -18.9, MB ~ -18.3) are consistent with a dwarf galaxy like the LMC. From the central SDSS spectrum of the host we estimate an oxygen abundance of 12 + log(O/H) = 8.3 using the Halpha/[N II] ratio (Pettini & Pagel 2004) and an H-alpha star-formation rate (Kennicutt 1998) of ~0.5 Msun/yr (approx. corrected for extinction).

For more information about the ASAS-SN project see ASAS-SN Homepage and also ASAS-SN Transients page.