Orbital Period Changes and Their Explanations in Two Algol Binaries: WY Per and RW Leo

Abstract

WY Per and RW Leo are two Algol-type binaries. Based on our new CCD observations and the almost century-long historical record of the times of primary eclipses for WY Per and RW Leo, the orbital period changes and their explanations were reanalyzed and rediscussed in detail. It has been found that the orbital period of WY Per shows a cyclic oscillation with a period of $P_{3} =$ 71.5 yr and a semiamplitude of $A_{3} =$ 0$^{\rm d}\!\!\!.$0739. The period variation can be interpreted by the light-travel time effect (LTTE) via the presence of a third body in an eccentric orbit with an eccentricity of $e_{3} \simeq$ 0.602 in the system. For RW Leo, its orbital period shows complex variations. Two cyclic variations (i.e., $P_{3} =$ 77.8 yr and $A_{3} =$ 0$^{\rm d}\!\!\!.$033, and $P_{4} =$ 39.1 yr and $A_{4} =$ 0$^{\rm d}\!\!\!.$022) were discovered. The cyclic variations of $P_{3} =$ 77.8 yr and $A_{3} =$ 0$^{\rm d}\!\!\!.$033 can be attributed to the LTTE via the presence of a third body in an eccentric orbit with an eccentricity of $e_{3} \simeq$ 0.732.