Marion, G. H.Brown, Peter J.Vinkó, JozsefSilverman, Jeffrey M.Sand, David J.Challis, PeterKirshner, Robert P.Wheeler, J. CraigBerlind, PerryBrown, Warren R.Calkins, Michael L.Camacho, YssavoDhungana, GovindaFoley, Ryan J.Friedman, Andrew S.Graham, Melissa L.Howell, D. AndrewHsiao, Eric Y.Irwin, Jonathan M.Jha, Saurabh W.Kehoe, RobertMacri, Lucas M.Maeda, KeiichiMandel, KaiseyMcCully, CurtisPandya, VirajRines, Kenneth J.Wilhelmy, StevenZheng, Weikang2019-09-252016Marion, G. H., Peter J. Brown, Jozsef Vinkó, Jeffrey M. Silverman, David J. Sand, Peter Challis, Robert P. Kirshner, et al. 2016. “SN 2012cg: EVIDENCE FOR INTERACTION BETWEEN A NORMAL SN Ia AND A NON-DEGENERATE BINARY COMPANION.” The Astrophysical Journal 820 (2): 92. https://doi.org/10.3847/0004-637x/820/2/92.0004-637X1538-4357http://nrs.harvard.edu/urn-3:HUL.InstRepos:41399813We report evidence for excess blue light from the Type Ia supernova (Sn Ia) SN. 2012cg at 15 and 16 days before maximum B-band brightness. The emission is consistent with predictions for the impact of the supernova on a non-degenerate binary companion. This is the first evidence for emission from a companion to a normal SN. Ia. Sixteen days before maximum light, the B - V color of SN. 2012cg is 0.2 mag bluer than for other normal SN. Ia. At later times, this supernova has a typical SN. Ia light curve, with extinction-corrected MB = -19.62 +/- 0.02 mag and Delta m(15)(B)= 0.86 +/- 0.02. Our data set is extensive, with photometry in seven filters from five independent sources. Early spectra also show the effects of blue light, and high-velocity features are observed at early times. Near maximum, the spectra are normal with a silicon velocity v(Si) = -10,500 km s(-1). Comparing the early data with models by Kasen favors a main-sequence companion of about six solar masses. It is possible that many other SN Ia have main-sequence companions that have eluded detection because the emission from the impact is fleeting and faint.en-USJournal Article2019-09-2510.3847/0004-637X/820/2/92