Possible Mass and Angular Momentum Loss in Algol-Type Binaries. V. RT Persei and TX Ursae Majoris

Abstract

The changes in the orbital periods of two EA-type eclipsing binaries, RT Per and TX UMa, are studied in detail, based on the analysis of their times of minimum light. For RT Per, it is shown that the trend of the O-C curve can be described by a parabola opening at the bottom, which indicates a secular period decrease at the rate dP/dt -9.29 x 10(-8) days yr(-1). By subtracting the secular decrease in the O-C curve, the residuals display an oscillatory variation that can either be described by a continuous periodic change, indicating the presence of a third body, or by several linear ephemerides, indicating several sudden period jumps. Since the oscillatory change is not strictly periodic, the latter is more plausible, which suggests that several irregular period jumps are superposed on the long-term period decrease. For the other object, TX UMa, it is discovered that the O-C trend also suggests a secular period decrease (dP/dt = -7.13 x 10(-7) days yr(-1)), and five irregular period jumps are found superposed on the secular period decrease. This kind of period is not unique for Algol-type binary systems. The period changes, both the secular decrease and the sudden jumps, can be plausibly explained by orbital angular momentum loss via magnetic coupling and gravity coupling between the components.