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The negligible eccentricity of all extra solar planets with periods less than six days can be accounted for by dissipation of tidal disturbances within their envelopes which are induced by their host stars. In the period range of 7-21 days, planets with circular orbits coexist with planets with eccentric orbits. These will be referred to as the borderline planets. We propose that this discrepancy can be attributed to the variation in spin-down rates of young stars. In particular, prior to spin-down, dissipation of a planets tidal disturbance within the envelope of a sufficiently rapidly spinning star can excite eccentricity growth, and for a more slowly spinning star, at least reduce the eccentricity damping rate. In contrast, tidal dissipation within the envelope of a slowly spinning low-mass mature star can enhance the eccentricity damping process. Based on these results, we suggest that short-period planets around relatively young stars may have a much larger dispersion in eccentricity than those around mature stars. We also suggest that because the rate of angular momentum loss from G and K dwarfs via stellar winds is much faster than the tidal transfer of angular momentum between themselves and their very-short (3-4 days) period planets, they cannot establish a dynamical configuration in which the stellar and planetary spins are approximately parallel and synchronous with the orbital frequency. In principle, however, such configurations may be established for planets (around G and K dwarfs) with orbital periods of up to several weeks. In contrast to G and K dwarfs, the angular momentum loss due to stellar winds is much weaker in F dwarfs. It is therefore possible for synchronized short-period planets to exist around such stars. The planet around Tau Boo is one such example.
We analyze data from the Quarter 1-17 Data Release 24 (Q1--Q17 DR24) planet candidate catalog from NASAs Kepler mission, specifically comparing systems with single transiting planets to systems with multiple transiting planets, and identify a distinc
Eclipsing binaries are observed to have a range of eccentricities and spin-orbit misalignments (stellar obliquities). Whether such properties are primordial, or arise from post-formation dynamical interactions remains uncertain. This paper considers
Recent discoveries of strongly misaligned transiting exoplanets pose a challenge to the established planet formation theory which assumes planetary systems to form and evolve in isolation. However, the fact that the majority of stars actually do form
We have analyzed data from Campaigns 0-5 of the K2 mission and report 19 ultra-short-period candidate planets with orbital periods of less than 1 day (nine of which have not been previously reported). Planet candidates range in size from 0.7-16 Earth
Spin evolution of X-ray pulsars in High Mass X-ray Binaries (HMXBs) is discussed under various assumptions about the geometry and physical parameters of the accretion flow. The torque applied to the neutron star from the accretion flow and equilibriu