Photospheric-Phase Spectropolarimetry and Nebular-Phase Flux Spectra of the Peculiar Type Ic Supernova 2002ap

The early-time optical spectrum of the Type Ic supernova (SN) 2002ap was characterized by unusually broad features, leading some authors to designate it a “hypernova. ” We present optical spectropolarimetry of this object 16 and 37 days after the estimated date of explosion. After correcting for interstellar polarization, we find evidence for a high level of intrinsic continuum polarization at both epochs: p � 1.3 % on day 16 and p � 1.0 % on day 37. Prominent line polarization is also seen, especially in the Ca II infrared triplet during the second epoch. When interpreted in terms of the oblate, electron-scattering model atmospheres of Höflich (1991), our results imply an asymmetry of at least 20% (day 16) and 17 % (day 37). The data suggest a fair degree of axisymmetric asymmetry in both epochs; however, the polarization angle is different by about 55 ◦ between the two epochs, implying a complex morphology for the thinning ejecta. We also present flux spectra of SN 2002ap taken 131 and 140 days after the