Optical spectropolarimetry of SN 2002ap: A high-velocity asymmetric explosion

We present spectropolarimetry of the Type Ic supernova SN 2002ap and give a preliminary analysis: the data were taken at two epochs, close to and 1 month later than the visual maximum (2002 February 8). In addition, we present June 9 spectropolarimetry without analysis. The data show the development of linear polarization. Distinct polarization profiles were seen only in the O I lambda7773 multiplet/Ca II IR triplet absorption trough at maximum light and in the O I lambda7773 multiplet and Ca II IR triplet absorption troughs a month later, with the latter showing a peak polarization as high as similar to2%. The intrinsic polarization shows three clear position angles: 80degrees for the February continuum, 120degrees for the February line feature, and 150degrees for the March data. We conclude that there are multiple asymmetric components in the ejecta. We suggest that the supernova has a bulk asymmetry with an axial ratio projected on the sky that is different from 1 by an order of 10%. Furthermore, we suggest very speculatively that a high-velocity ejecta component moving faster than similar to0.115c (e.g., a jet) contributes to polarization in the February epoch.