G. H. Marion, Peter J. Brown, Jozsef Vinkó, Jeffrey M. Silverman, David J. Sand, Peter Challis, Robert P. Kirshner, J. Craig Wheeler, Perry Berlind, Warren R. Brown, Michael L. Calkins, Yssavo Camacho, Govinda Dhungana, Ryan J. Foley, Andrew S. Friedman, Melissa L. Graham, D. Andrew Howell, Eric Y. Hsiao, Jonathan M. Irwin, Saurabh W. JhaRobert Kehoe, Lucas M. Macri, Keiichi Maeda, Kaisey Mandel, Curtis McCully, Viraj Pandya, Kenneth J. Rines, Steven Wilhelmy, Weikang Zheng

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76 Citations (Scopus)


We 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 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 mag and . 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 vSi = -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.

Original languageEnglish
Article number92
JournalAstrophysical Journal
Issue number2
Publication statusPublished - Apr 1 2016


  • supernovae: general
  • supernovae: individual (2012cg)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Marion, G. H., Brown, P. J., Vinkó, J., Silverman, J. M., Sand, D. J., Challis, P., Kirshner, R. P., Wheeler, J. C., Berlind, P., Brown, W. R., Calkins, M. L., Camacho, Y., Dhungana, G., Foley, R. J., Friedman, A. S., Graham, M. L., Howell, D. A., Hsiao, E. Y., Irwin, J. M., ... Zheng, W. (2016). SN 2012cg: EVIDENCE for INTERACTION between A NORMAL SN Ia and A NON-DEGENERATE BINARY COMPANION. Astrophysical Journal, 820(2), [92].