The impact of the oblateness of Regulus on the motion of its companion
Abstract
The fast spinning B-star Regulus has recently been found to be orbited by a fainter companion in a close circular path with orbital period Pb = 40.11(2) d. Being its equatorial radius Re 32% larger than the polar one Rp, Regulus possesses a remarkable quadrupole mass moment Q. We investigate the effects of Q on the orbital period Pb of its companion in order to see if they are measurable, given the present-day level of accuracy in measuring Pb. Conversely, we will look for deviations from the third Kepler law, attributed to the quadrupole mass moment Q of Regulus, to constrain the ratio γ=m/M of the system's masses.
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