Supernova 2011ga in Pgc 69458 = Psn J22402742+0311580
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2011
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Abstract
Report the discovery of an apparent supernova in unfiltered Catalina Sky Survey (CSS) images: SN 2011 UT R.A. (2000.0) Decl. Mag. Offset 2011ga Sep. 18.25 22 40 27.42 + 3 11 58.0 17.3 18".2 W, 7".4 N The new object was designated PSN J22402742+0311580 when it was posted at the Central Bureau's TOCP webpage and is here designated SN 2011ga based on the spectroscopic report below. Additional CCD magnitudes for 2011ga (unfiltered unless noted otherwise: July 2.38 UT, [19.3 (CSS); Sept. 19.179, 16.5 (Joseph Brimacombe, Cairns, Australia; infrared filter, wavelength > 700 nm; image posted at URL http://www.flickr.com/photos/43846774@N02/6177998402/); 19.320, 17.2 (Brimacombe; position end figures 27s.38, 58".9; image posted at website URL http://www.flickr.com/photos/43846774@N02/6168832131/). S. Valenti, S. Benetti, L. Tomasella, and P. Ochner, Osservatorio Astronomico di Padova, Istituto Nazionale di Astrofisica; and A. Pastorello, Dipartimento di Astronomia, Universita di Padova, on behalf of a larger collaboration, report that a spectrogram of PSN J22402742+0311580 = SN 2011ga, obtained on Sept. 24.91 UT, suggests that it is a type-Ia supernova observed close to B-band maximum. The velocity of the ejected material, as deduced from the position of the minimum of the Si II lines, is about 10600 km/s. G. H. Marion, Harvard-Smithsonian Center for Astrophysics (CfA), on behalf of the CfA Supernova Group, report that a spectrum (range 340-740 nm) of PSN J22402742+0311580 = 2011ga was obtained on Sept. 27 UT by Marion with the F. L. Whipple Observatory 1.5-m telescope (+ FAST). Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows that the object is a type-Ia supernova a few days after maximum light. The best-fit template spectrum is that of SN 2003du at +2 days. The velocity of the Si II 635.5-nm feature is estimated to be approximately 10800 km/s, using the SNID estimated redshift of z = 0.040....