2001AJ....121.1614Q

Orbital period variations of eight Algol-type binaries, TU Cnc, FZ Del, AY Gem, VZ Leo, FH Ori, IU Per, XZ Per, and BE Vul, are studied based on the analysis of the O-C observations. It is discovered that the periods of three systems, TU Cnc, FH Ori, and IU Per, show secular decrease. For AY Gem and XZ Per, the orbital periods can be described by a sudden decrease or by two sudden changes superposed on a secular decrease. Weak evidence also shows that the orbital periods of the other three systems, FZ Del, VZ Leo, and BE Vul, are decreasing. As in other systems proposed by Qian, the decrease in the orbital periods of these systems, combined with their semidetached configurations, suggests that they may be undergoing secular mass and angular momentum loss due to magnetic braking. The irregular period jumps superposed on the secular decrease (e.g., in AY Gem, FH Ori, XZ Per, and BE Vul) can be explained by variable magnetic coupling and gravity coupling between the two components. However, the present secular period decrease of these systems may be part of a long-period periodic change (as in TT Del), which needs further investigation.