Orbital period changes and possible stellar wind mass loss in the algol-type binary system AT Pegasi

An analysis of the measurements of mid-eclipse times of AT Peg has been presented. It indicates a period decrease rate of dP/dt = −4.2 × 10−7 d/yr, which can be interpreted in terms of mass loss from the system via stellar wind with a rate between (1 and 2) × 10−8 Mʘ/yr. The O–C diagram shows a growing sine wave covering two different cycles of 13 yr and 31.9 yr with amplitudes equal to 0.026 and 0.032 day, respectively. These unequal durations of the cycles may be explained by magnetic activity cycling variations due to star spots. The obtained characteristics of the second cycle are consistent with similar systems when applying Applegate’s mechanism.