Polarization data in the q − u plane for SN 1998S at ∼5 d after explosion, from L00. Photons with wavelengths corresponding to the broad wings and narrow-line core of the Hα flux profile are indicated with red and green circles, respectively. Each point represents a bin 10 Å wide, except for the green circles, which are binned at 2 Å for enhanced resolution. The blue line spans the range of potential ISP choices derived from different assumptions about the extent of depolarization in the narrow-line core region of Hα. The blue squares indicate four specific choices of ISP discussed in the text, which yield the inferred intrinsic polarizations displayed in the bottom panels of Fig. 4. See Sect. 4 for a discussion.