Algol variable

An Algol binary is a system where both stars are near-spherical such that the timing of the start and end of the eclipses is well-defined.

[1] When the cooler component passes in front of the hotter one, part of the latter's light is blocked, and the total brightness of the binary, as viewed from Earth, temporarily decreases.

Total brightness may also decrease, but less so, when the hotter component passes in front of the cooler one; this is the secondary minimum.

Most Algol variables are quite close binaries, and therefore their periods are short, typically a few days.

[3] Component stars of Algol binary systems have a spherical, or slightly ellipsoidal shape.

Phase-folded light curve of the Algol variable Zeta Phoenicis recorded by NASA's Transiting Exoplanet Survey Satellite (TESS)