On the Third‐Body Hypothesis of the Eclipsing Binary AS Camelopardalis

Abstract

This is the second paper concerned with the third-body hypothesis, proposed to give a possible explanation of the apsidal motion anomalies of AS Cam, one of the binaries providing the rare opportunity to test general relativity. The perturbations in orbital elements of AS Cam and their photometric consequences (the secondary minimum phase variations, changes in depths of eclipses, etc.) were studied by the same numerical scheme as in the case of DI Her by Khaliullin, Khodykin, and Zakharov. The various constraints, based on the photometric observations, and the triple system stability criteria were considered, and the ranges of third-body parameters are presented. The hypothetical nearby companion—a main-sequence K0-F2 star with moderate mass (0.78-1.45 M☉) revolving in a highly inclined ( > 32°) short-period orbit (P' = 0.6-2.9 yr)—is found to be able to increase the orbital eccentricity of AS Cam. The perturbation in e of the order (de/dt)tb = 7 × 10-4 yr-1 results in the observed change in the displacement of the time of secondary minimum from that of primary minimum that prevents the apsidal motion rate from being detected correctly. Several observational tests that could possibly either verify or refute the third-body hypothesis of AS Cam are discussed.