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Special Notice #283: Supernova 2012cg IN NGC 4424 = PSN J12271283+0925132

May 23, 2012: IAU Central Bureau Electronic Telegram 3111 (Daniel W. E. Green, ed.) announces the LOSS discovery (reported by M. Kandrashoff, S. B. Cenko, W. Li, and A. V. Filippenko) of a supernova in NGC 4424 on 2012 May 17.22 at unfiltered magnitude 16.9.

Spectra indicating the object to be a Type Ia supernova discovered about two weeks before maximum were obtained 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 on 2012 May 18 UT and reported by S. B. Cenko, A. V. Filippenko, and J. M. Silverman (University of California, Berkeley), and A. Gal-Yam (Weizmann Institute of Science); and

 - J. Irwin with the F. L. Whipple Observatory 1.5-m telescope (+ FAST) on 2012 May 18 UT and reported by 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.

SN 2012cg was initially designated PSN J12271283+0925132 when it was posted on the Central Bureau's TOCP webpage (

Unfiltered magnitude 16.9 at discovery, SN 2012cg has brightened to magnitude 12.90 CR, according to the following observations submitted to the AAVSO International Database:

2012 May 18.8823 UT, 15.01 CV +/-0.03 (S. Howerton, Arkansas City, KS);
20.0980, 14.348 V +/-0.012 (K. Graham, Manhattan, IL);
20.1051, 13.698 I +/-0.012 (Graham);
20.1121, 13.974 R +/-0.008 (Graham);
20.1191, 14.755 B +/-0.017 (Graham);
20.1261, 14.320 V +/-0.011 (Graham);
20.1331, 13.676 I +/-0.011 (Graham);
20.1402, 13.975 R +/-0.009 (Graham);
20.1472, 14.743 B +/-0.018 (Graham);
20.1542, 14.260 V +/-0.012 (Graham);
20.1612, 13.543 I +/-0.013 (Graham);
20.1683, 13.935 R +/-0.011 (Graham);
20.1753, 14.604 B +/-0.020 (Graham);
20.2118, 14.38 V +/-0.04 (Howerton);
21.1927, 14.02 V +/-0.04 (Howerton);
21.8958, 13.9 (K. Wenzel, Grossostheim, Germany);
22.9347, 12.90 CR +/-0.01 (J.-L. Gonzalez Carballo, Badajoz, Spain);

Additional observations are available in CBET 3111.

Coordinates: RA 12 27 12.83  Dec +09 25 13.2 (2000.0)

Additional position end figures are provided by J. Brimacombe, Cairns, Australia (12.84s, 13.1"; image posted at; M. Martignoni, Magnago, Italy (12.82s, 12.9"); F. Luppi and L. Buzzi, Varese, Italy (12.84s, 13.1"; image posted at

Charts for SN 2012cg may be created using the AAVSO Variable Star Plotter (

Observations of SN 2012cg should be submitted to the AAVSO using the name "SN 2012cg".

This AAVSO Special Notice was compiled by Elizabeth O. Waagen.


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