Thursday, September 24, 2015

Accutely Characterizing the WASP-33 System

Accurate characterization of the stellar and orbital parameters of the exoplanetary system WASP-33 b from orbital dynamics




By using the most recently published Doppler tomography measurements and accurate theoretical modeling of the oblateness-driven orbital precessions, we tightly constrain some of the physical and orbital parameters of the planetary system hosted by the fast rotating star WASP-33. In particular, the measurements of the orbital inclination ip to the plane of the sky and of the sky-projected spin-orbit misalignment λ at two epochs six years apart allowed for the determination of the longitude of the ascending node Ω and of the orbital inclination I to the apparent equatorial plane at the same epochs. As a consequence, average rates of change Ω˙exp, I˙exp of this two orbital elements, accurate to a ≈10−2 deg yr−1 level, were calculated as well. By comparing them to general theoretical expressions Ω˙J2, I˙J2 for their precessions induced by an arbitrarily oriented quadrupole mass moment, we were able to determine the angle i⋆ between the star's spin S and the line of sight and its first even zonal harmonic J⋆2 obtaining

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