Supernova 2012cg in NGC 4424 = Psn J12271283+0925132
Abstract
Further to CBET 3105, M. Kandrashoff, S. B. Cenko, W. Li, and A. V. Filippenko report the LOSS discovery of an apparent supernova on unfiltered KAIT images: SN 2012 UT R.A. (2000.0) Decl. Mag. Offset 2012cg May 17.22 12 27 12.83 + 9 25 13.2 16.9 17".3 E, 1".5 S The variable was designated PSN J12271283+0925132 when it was posted at the Central Bureau's TOCP webpage and is here designated SN 2012cg based on the spectroscopic confirmation reported below. Additional CCD magnitudes for 2012cg (unfiltered unless noted otherwise): May 12.30 UT, [18.5 (KAIT); 14.87, [19.0 (G. Cortini, Predappio, Italy; Celestron C14 telescope + Starlight X-Press SXVR H9 camera); 17.26, 16.8 (KAIT); 18.332, 14.9 (Joseph Brimacombe, Cairns, Australia; luminance filter; position end figures 12s.84, 13".1; image posted at http://www.flickr.com/photos/43846774@N02/7225356298/); 18.840, R_c = 15.1 (Massimiliano Martignoni, Magnago, Italy; 0.25-m f/10 reflector; position end figures 12s.82, 12".9); 18.89, 15.2 (Cortini); 18.975, 14.9 (Federica Luppi and Luca Buzzi, Varese, Italy; 0.38-m f/6.8 reflector; position end figures 12s.84, 13".1; reference stars from CMC-14 catalogue; image posted at http://www.astrogeo.va.it/pub/TOCP/PSN_N4424.jpg). S. B. Cenko, A. V. Filippenko, and J. M. Silverman, University of California, Berkeley; and A. Gal-Yam, Weizmann Institute of Science, report that a CCD spectrum (range 340-800 nm) obtained on May 18 UT by L. Pei, M. Nguyen, D. Carson, and A. J. Barth (University of California, Irvine) with the Kast double spectrograph on the Shane 3-m telescope at Lick Observatory shows that 2012cg is probably a very young type-Ia supernova. The spectrum resembles that of SN 1990N about two weeks before maximum brightness (Leibundgut et al. 1991, Ap.J. 371, L23). Intensive follow-up observations at all wavelengths are encouraged. G. H. Marion, R. P. Kirshner, and R. J. Foley, Harvard-Smithsonian Center for Astrophysics (CfA); and P. Challis, Australian National University, on behalf of the CfA Supernova Group, report that a spectrum (range 340-740 nm) of PSN J12271283+0925132 = 2012cg was obtained on May 18 UT by J. Irwin 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 very early type-Ia supernova. A fit is found to the template of SN 1990N at -13 days. Na I D and Ca II H and K interstellar lines are quite strong in the spectrum from 2012cg but the region near 420.0 nm is much shallower than the deep absorption at this wavelength in the template spectrum from SN 1990N at -13 days. The Si II 635.5-nm absorption feature of 2012cg has two components at approximately 21000 and 11000 km/s with the high-velocity component being stronger. Using a redshift of z = 0.001458 for NGC 4424 (Kent et al. 2008, A.J. 136, 713).
- Publication:
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Central Bureau Electronic Telegrams
- Pub Date:
- May 2012
- Bibcode:
- 2012CBET.3111....1K