Spectroscopic Evidence for Nonuniform Starspot Properties on II Pegasi

Abstract

We present spectroscopic evidence for multiple spot temperatures on the RS CVn star II Pegasi (HD 224085). We model the strengths of the 7055 and 8860 A TiO absorption bands in the spectrum of II Peg using weighted sums of inactive comparison spectra: a K star to represent the nonspotted photosphere and an M star to represent the spots. The best fit yields independent measurements of the starspot filling factor ( fS ) and mean spot temperature () averaged over the visible hemisphere of the star. During three-fourths of a rotation of II Peg in late 1996, we measure a constant fS~55%+/-5% . However, varies from 3350+/-60 to 3550+/-70 K. We compute for two simple models: (1) a star with two distinct spot temperatures, and (2) a star with different umbral/penumbral area ratios. The changing correlates with emission strengths of H alpha and the Ca II infrared triplet in the sense that cooler accompanies weaker emission. We explore possible implications of these results for the physical properties of the spots on II Peg and for stellar surface structure in general.