Discovery of eclipse polarization in Algol.

The first detection of the stellar limb polarization predicted by Chandrasekhar in 1946 in an eclipsing binary system is reported. Observations of linear polarization of the bright star Algol were made in unifiltered light over a passband of roughly 1000-5500 A, concentrated around the times of primary eclipse from December 1980 to February 1983. An eclipse polarization was isolated that has a full amplitude of 0.01 percent, and a phase-dependent pattern in agreement with that expected for the Chandrasekhar mechanism. Results also support the contention that the binary AB and third-star AB-C orbits in Algol are nearly perpendicular to each other.