No abstract

We investigate the spin behaviour of close-in rocky planets and the implications for their orbital evolution. Considering that the planet rotation evolves under simultaneous actions of the torque due to the equatorial deformation and the tidal torque, both raised by the central star, we analyse the possibility of temporary captures in spin-orbit resonances.The results of the numerical simulations of the exact equations of motions indicate that, whenever the planet rotation is trapped in a resonant motion, the orbital decay and the eccentricity damping are faster than the ones in which the rotation follows the so-called pseudosynchronization. Analytical results obtained through the averaged equations of the spin-orbit problem show a good agreement with the numerical simulations.We apply the analysis to the cases of the recently discovered hot super-Earths Kepler-10 b, GJ 3634 b and 55 Cnc e. The simulated dynamical history of these systems indicates the possibility of capture in several spin-orbit resonances; particularly, GJ 3634 b and 55 Cnc e can currently evolve under a non-synchronous resonant motion for suitable values of the parameters. Moreover, 55 Cnc e may avoid a chaotic rotation behaviour by evolving towards synchronization through successive temporary resonant trappings.

No abstract

This paper considers the dynamics of two planets, as the planets B and C of the pulsar PSR B1257+12, near a 3/2 mean-motion resonance. A two-degrees-of-freedom model, in the framework of the general three-body planar problem, is used and the solutions are analyzed through surfaces of section and Fourier techniques in the full phase space of the system.

Context. During the first hundred million years after the formation of our solar system, the four giant planets are believed to have migrated significantly (by up ≈20 AU). The current scenario and dynamics of the satellites of these planets must be the result of both the initial conditions of their formation and this early extensive migrational episode. Aims. We examine the effects of the migration on the primordial satellites of Uranus. Methods. We use the Nice model to generate templates for the evolution of the four giant planets and record the time history of these planets and important close encounters. The satellites are then added to Uranus and these objects are integrated according to the dynamics stored in the templates. Results. We show that Oberon is the outermost regular satellite of Uranus that is able to resist the close encounters during the extensive migrational episode. Some theories predict that Uranus' satellites can form out to a 57 R U distance from the planet, but we show that even those at ≈27 R U from the planet cannot support the instabilities that appeared during migration. Close objects, such as the current regular satellites of Uranus, can survive quite stably and we are able to place some constraints on the masses of the planetesimals that have close encounters. For instance, if an object with mass ≥10 −9 M approaches at distances < ∼ 23 R U from Uranus, the regular satellites can be destabilized or their eccentricities or inclinations excited to some non-compatibles values. We also find that planet-planetesimal close encounters can generate capture. In this way, we present a promising means of explaining the origin of the irregular satellites of Uranus. The importance of the oblateness of the planet, and the Sun for just-captured planetesimals is also shown.