Evidences of spin-orbit resonance among spectroscopic binary stars

Abstract

A spin-orbit resonance occurs when the periods of rotation and orbital revolution of a celestial body have a ratio which commensurate and this is stable. Observations of the rotational synchronize in binary stars of few days periods and circular orbits confirm 1/1 spin-orbit resonance. Also, observations of the rotational synchronism at periastron in eccentric binaries whose eccentricities satisfy a criterion for spin-orbit resonance, indicate resonance values larger than 1/1. On the other hand, the histograms made by the present author with data from the Seventh Catalogue of the Orbital Elements of binaries whose revolution periods are between 10 to 30 days, shown an unusual accumulation of stars near the eccentricity e=0.19, which belongs to 3/2 spin-orbit resonance. We presume this confirms such resonance. Furthermore, our histograms suggest some accumulation of stars near the eccentricity, e=0.30, which belongs to 5/2 spin-orbit resonance.