Effects of Magnetic Braking and Tidal Friction on Hot Jupiters - Astrophysics > Earth and Planetary AstrophysicsReport as inadecuate




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Abstract: Tidal friction is thought to be important in determining the long-termspin-orbit evolution of short-period extrasolar planetary systems. Using asimple model of the orbit-averaged effects of tidal friction Eggleton, Kiselevaand Hut 1998, we analyse the effects of the inclusion of stellar magneticbraking on the evolution of such systems. A phase-plane analysis of asimplified system of equations, including only the stellar tide together with amodel of the braking torque proposed by Verbunt and Zwaan 1981, is presented.The inclusion of stellar magnetic braking is found to be extremely important indetermining the secular evolution of such systems, and its neglect results in avery different orbital history. We then show the results of numericalintegrations of the full tidal evolution equations, using the misaligned spinand orbit of the XO-3 system as an example, to study the accuracy of simpletimescale estimates of tidal evolution. We find that it is essential toconsider coupled evolution of the orbit and the stellar spin in order to modelthe behaviour accurately. In addition, we find that for typical Hot Jupitersthe stellar spin-orbit alignment timescale is of the same order as the inspiraltime, which tells us that if a planet is observed to be aligned, then itprobably formed coplanar. This reinforces the importance of Rossiter-McLaughlineffect observations in determining the degree of spin-orbit alignment intransiting systems.



Author: A.J. Barker, G.I. Ogilvie

Source: https://arxiv.org/







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