Starspot areas and temperatures in nine binary systems with late-type components

Abstract

A computer program that generates light curves for rotating spotted stars has been used to solve multicolor light curves of BY Dra, II Peg, HK Lac, HR 7275, IM Peg, λ And, UX Ari, σ Gem, and LX Per. The flux ratio of spot to photosphere in the photometric bands was determined from a revision of the Barnes-Evans relations. One or two circular spots could accurately reproduce the photometric behavior for most of these systems. The wavelength dependence of limb darkening was found to contribute a surprisingly large amount of the variation in the visible colors. The changes in the spot activity on II Peg were followed from 1976 through 1982. Definite spot temperatures were derived for most of the systems. The temperature of the spots ranges from 4050 to 3330K, while the temperature of the unspotted photospheres of the stars varied by only about 400K. The data suggest that the spots consist primarily of material at a single temperature, and that they are not divided into roughly equal amounts of umbral and penumbral material.