Spectropolarimetry of the Type Ia supernova 2012fr

• Published in: Monthly notices of the Royal Astronomical Society. Letters 2013-07, Vol.433 (1), p.L20-L24
• Main Authors: Maund, J. R., Spyromilio, J., Höflich, P. A., Wheeler, J. C., Baade, D., Clocchiatti, A., Patat, F., Reilly, E., Wang, L., Zelaya, P.
• Format: Article
• Language: English
• ISSN: 1745-3925; 1745-3933
• DOI: 10.1093/mnrasl/slt050

Spectropolarimetry provides the means to probe the 3D geometries of supernovae (SNe) at early times. We report spectropolarimetric observations of the Type Ia SN 2012fr at four epochs: −11, −5, +2 and +24 d, with respect to B-light-curve maximum. SN 2012fr is a normal Type Ia SN, similar to SNe 1990N, 2000cx and 2005hj (that all exhibit low velocity decline rates for the principal Si ii line). The SN displays high-velocity components at −11 d that are highly polarized. The polarization of these features decreases as they become weaker from −5 d. At +2 d, the polarization angles of the low-velocity components of silicon and calcium are identical and oriented at 90° relative to the high-velocity Ca component. In addition to having very different velocities, the high- and low-velocity Ca components have orthogonal distributions in the plane of the sky. The continuum polarization for the SN at all four epochs is low,