Multiple Probes of the AS Cam Dynamical Problem

Abstract

AbstractAS Camelopardalis is notorious for its apparent disregard for the theory of apsidal motion. The orbit of this 3.43-day double-lined eclipsing binary (B8V + B9.5V) rotates approximately 15° per century, which is only 0.3 to 0.4 as fast as predicted (classical + relativistic). Our dynamical program explores, as have others, the suggestion that a third star perturbs the orbit of the eclipsing pair and slows its apsidal motion, dω/dt. On the observational side, we unify the process of extracting apsidal motion and light-time effect parameters from eclipse minima by directly including a third body light-time effect along with the usual ephemeris parameters. By numerical experiment we identify third body parameters consistent with the eclipse timings and with the dynamics of third body perturbations. Results include the minimum third body mass required to produce the given retrograde apsidal rate. Finally, we use a general binary star light curve program that includes a light-time effect to solve for dω/dt and ephemeris parameters together with other quantities, combining 21 years of radial velocities and light curves within one coherent analysis. The program has an improved stellar atmosphere routine based on Legendre polynomials that have been fitted to Kurucz atmosphere models. By analyzing whole light curves, the program has access to more information than only times of minima. Results agree well with those from eclipse timings over 100 years and attain smaller standard errors despite utilizing only one-fifth of the traditional method’s baseline in time.