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ASAS-SN Discovery and Spectroscopic Classification of SN Ia at z=0.027

ATel #5363; J. L. Prieto (Princeton), N. Morrell (LCO), P. Lira (U. Chile), K. Z. Stanek, B. J. Shappee, C. S. Kochanek, 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)
on 4 Sep 2013; 21:53 UT
Credential Certification: Jose L. Prieto (jose@obs.carnegiescience.edu)

Subjects: Optical, Supernovae, Transient

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 optical transient:

Object         RA(J2000)      Dec(J2000)    Disc. UT Date    Disc. V Mag 
ASASSN-13cu   00:40:09.93    -10:26:21.9      Sep. 1.43        17.0 
The transient was discovered on images obtained UT Sep. 1.43 and confirmed on Sep. 3 and Sep 4, close to the detection limit. The source is seen in images obtained Aug. 29 and undetected in earlier images (V > 17). Confirmation images were also obtained by N. Morrell on Sep 4.24 with WFCCD mounted on the du Pont 2.5m telescope at LCO. The transient is detected at RA = 00:40:10.14 and DEC = -10:26:25.90, with B = 17.58 +/- 0.03 and V = 17.04 +/- 0.03 mag. The WFCCD confirmation images are shown here. ASASSN-13cu is located 0.2" N and 6.0" W of the center of its spiral host galaxy SDSS J004010.55-102626.1 (z=0.0272, d=107 Mpc via NED), which implies an absolute V mag. of -18.2 (mu=35.15 mag; A_V=0.094 from Schlafly & Finkbeiner 2011) and a projected distance from the host center of 3.1 kpc.

An optical spectrum (range 3700-9200 Angs.; resolution 7 Angs.) of ASASSN-13cu was obtained on UT Sep 4.2 with du Pont + WFCCD. The spectrum is that of a normal Type Ia SN past peak. Cross-correlation with a library of SN spectra using SNID (Blondin & Tonry 2007) gives good correlations with normal SN Ia at 10 days after maximum. After correcting for the host galaxy redshift, we measure a Si II 6355 velocity of -9800 km/s. A plot of the spectrum can be found here.

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