Determination of tidal distortion in the eclips- ing binary system V621 Cen by means of deviations from the third Kepler law

In this paper we determine the tidal distortion parameter km of the secondary partner (mass loser) of the semi-detached eclipsing binary system V621 Cen by comparing the phenomenologically determined orbital period Pb = 3.683549(11) to the Keplerian one P Kep computed with the values of the relevant system’s parameters determined independently of the third Kepler law itself. Our result is km = −1.5±0.6. Using the periastron precession, as traditionally done with other eclipsing binaries in eccentric orbits, would have not been possible because of the circularity of the V621 Cen path.