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Paper: II Peg: Spectroscopic Evidence for Multiple Starspot Temperatures
Volume: 154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop
Page: 1439
Authors: O'Neal, Douglas; Saar, Steven H.; Neff, James E. Neff
Abstract: We present spectroscopic evidence for multiple spot temperatures on the RS CVn star II Pegasi (HD 224085). We fit the strengths of the 7055 AAg and 8860 AAg TiO absorption bands in the spectrum of an active star using weighted sums of comparison spectra: the spectrum of an inactive K star to represent the non-spotted photosphere and the spectrum of an M star to represent the spots. We can thus independently measure starspot filling factor (fspot) and temperature (tspot). During 3/4 of a rotation of II Peg in Sept.-Oct. 1996, we measure fspot approximately constant at 55+/-5%. However, tspot varies from 3350 K to 3500 K. Since our method yields one derived tspot integrated over the visible hemisphere of the star, we present the results of simple models of a star with two distinct spot temperatures and compute the tspot we would derive in those cases. The changing tspot correlates with emission strengths of Hα and the Ca 2 infrared triplet, in the sense that cooler \tspot accompanies weaker emission. We explore the consequences of these results for the physical properties of the spots on II Peg and for stellar surface structure in general.
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