Photometric Studies of the Triple Star ER Orionis

Abstract

A total of 1637 BVR CCD observations of the overcontact binary ER Ori are used as the basis for new light curves, including the first red one. From these measurements, new timings of minimum light have been calculated. The complex period variation can be sorted into a linear period improvement, a secular period increase of considerable magnitude, and a 50 year cyclical component. This latter is discussed in terms of a light-time contribution from a bound third star, which finds some support from Hipparcos results. The new light curves were synthesized using the Wilson-Divinney code. It was found useful to model a single modest spot in order to minimize the residuals from the observations. Our model is found to agree with previous light curves.