Document Type

Article

Publication Date

3-22-2016

Abstract

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.

Publication Title

The Astrophysical Journal

Volume

820

Issue

2

Required Publisher's Statement

© 2016 The American Astronomical Society

doi:10.3847/0004-637X/820/2/92

Link to publisher version of article: http://iopscience.iop.org/article/10.3847/0004-637X/820/2/92/meta;jsessionid=7F3245691B65574D028341AB2E61C33E.c3.iopscience.cld.iop.org

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