On the thermal bulges of exoplanets

Close-in exoplanets receive more stellar irradiation, implying that the thermal tidesn these planets may not be negligible compared to the gravitational tides. To investigatehe properties of the atmospheric thermal tides excited by the irradiation from their parenttars, we perform a linear analysis to study the atmospheric perturbations of exoplanets.he torque due to the thermal tides acting on the spin of the planet is estimated andompared to that due to the gravitational tides. In particular, we study the thermal tidesn a hypothetical super-Earth with a hydrogen-rich atmosphere at about 0:47 AU from a Sunliketar and those in the radiative layer of the hot Jupiter HD 209458b. In the super-Earthase, the torques arising from both tides can be cancelled out in some ranges of forcingeriods, inferring that the super-Earth may have been escaped from the stage of beingidally locked by its parent star. In the case of gaseous planets, the thermal bulges haveeen argued not to exist in the literature. However, our study suggests that the thermalulges could form when the thermal variations of the atmosphere are not hydrostaticallyalanced by the redistribution of gas in the layer near the turning point of internal waves.n some ranges of forcing periods and Q-values, both torques can be cancelled out inhe case of the hot Jupiter HD 209458b. The results imply that some of the close-inxoplanets, including both super-Earths and gaseous planets, may not lie in synchronouslyotating states at their ages of serveral Gyrs.