Interpretation of epsilon Aurigae. III. Study of the light curve based on disk models

The light curve expected from the eclipse of a star by a companion possessing a semitransparent disk has been investigated. Two computational procedures for deriving the light curve based on the geometrically thin-disk model are given here. Using these procedures, we have calculated the light curves of e Aur based on different sets of parameters including those given previously by Wilson. We have also studied the light curve of E Aur based on a geometrically thick disk model, and have advanced two proposals in order to understand the change in the shape of the light curve from one eclipse to the next, namely, (1) the rapid evolution that occurs in the disk and (2) the density waves in the disk and/or individual condensations that are revolving around the secondary each in an independent way. Whether the disk is thin or thick, we have shown that the observed light curve and the opacity distribution in the disk are related by an integral equation. Consequently, once the thickness is given, the fitting of the light c'irve is basically a question of assigning the opacity distribution to the disk, and vice versa. Subject headings: circumstellar shells - eclipsing binaries - stars, individual