An irregularity in the radial-velocity curve of an eclipsing spectroscopic binary immediately before and after eclipse; also known as the rotation effect. In most binaries the stars orbit in the same direction as they rotate on their axes. Immediately before maximum eclipse, the small segment of the star that remains uncovered therefore has a radial velocity that is directed away from the observer. The opposite applies as the star emerges from eclipse. The effect shows up as a short-lived rise and fall on the radial-velocity curve. It is named after the American astronomer Richard Alfred Rossiter (1886–1977).
Subjects: Astronomy and Astrophysics.