1,539 research outputs found
The silicate model and carbon rich model of CoRoT-7b, Kepler-9d and Kepler-10b
Possible bulk compositions of the super-Earth exoplanets, CoRoT-7b,
Kepler-9d, and Kepler-10b are investigated by applying a commonly used silicate
and a non-standard carbon model. Their internal structures are deduced using
the suitable equation of state of the materials. The degeneracy problems of
their compositions can be partly overcome, based on the fact that all three
planets are extremely close to their host stars. By analyzing the numerical
results, we conclude: 1) The iron core of CoRoT-7b is not more than 27% of its
total mass within 1 mass-radius error bars, so an Earth-like
composition is less likely, but its carbon rich model can be compatible with an
Earth-like core/mantle mass fraction; 2) Kepler-10b is more likely with a
Mercury-like composition, its old age implies that its high iron content may be
a result of strong solar wind or giant impact; 3) the transiting-only
super-Earth Kepler-9d is also discussed. Combining its possible composition
with the formation theory, we can place some constraints on its mass and bulk
composition.Comment: 20 pages, 8figures, accepted for publication in RAA. arXiv admin
note: text overlap with arXiv:0707.289
Secular dynamics of stellar spin driven by planets inside Kozai-Lidov resonance
In many exoplanetary systems with `hot Jupiters', it is observed that the
spin axes of host stars are highly misaligned to planetary orbital axes. In
this study, a possible channel is investigated for producing such a
misalignment under a hierarchical three-body system where the evolution of
stellar spin is subjected to the gravitational torque induced from the planet
inside Kozai--Lidov (KL) resonance. In particular, two special configurations
are explored in detail. The first one corresponds to the configuration with
planets at KL fixed points, and the second one corresponds to the
configurations with planets moving on KL librating cycles. When the planet is
located at the KL fixed point, the corresponding Hamiltonian model is of one
degree of freedom and there are three branches of libration centres for stellar
spin. When the planet is moving on KL cycles, the technique of Poincar\'e
section is taken to reveal global structures of stellar spin in phase space. To
understand the complex structures, perturbative treatments are adopted to study
rotational dynamics. It shows that analytical structures in phase portraits
under the resonant model can agree well with numerical structures arising in
Poincar\'e sections, showing that the complicated dynamics of stellar spin are
governed by the primary resonance under the unperturbed Hamiltonian model in
combination with the 2:1 (high-order and/or secondary) spin-orbit resonances.Comment: 15 pages, 11 figures. Accepted for publication in MNRA
The Pseudoscalar Meson and Heavy Vector Meson Scattering Lengths
We have systematically studied the S-wave pseudoscalar meson and heavy vector
meson scattering lengths to the third order with the chiral perturbation
theory, which will be helpful to reveal their strong interaction. For
comparison, we have presented the numerical results of the scattering lengths
(1) in the framework of the heavy meson chiral perturbation theory and (2) in
the framework of the infrared regularization. The chiral expansion converges
well in some channels.Comment: 10 pages, 1 figures, 4 tables. Corrected typos, Improved numerical
results, and More dicussions. Accepted for publication by Phys.Rev.
Making hot Jupiters in stellar clusters II: efficient formation in binary systems
Observations suggested that the occurrence rate of hot Jupiters (HJs) in open
clusters is largely consistent with the field () but in the
binary-rich cluster M67, the rate is . How does the cluster
environment boost HJ formation via the high-eccentricity tidal migration
initiated by the extreme-amplitude von Zeipel-Lidov-Kozai (XZKL) mechanism
forced by a companion star? Our analytical treatment shows that the cluster's
collective gravitational potential alters the companion's orbit slowly, which
may render the star-planet-companion configuration XZKL-favourable, a
phenomenon only possible for very wide binaries. We have also performed direct
Gyr -body simulations of the star cluster evolution and XZKL of planets'
orbit around member stars. We find that an initially-single star may acquire a
companion star via stellar scattering and the companion may enable XZKL in the
planets' orbit. Planets around an initially-binary star may also be
XZKL-activated by the companion. In both scenarios, the companion's orbit has
likely been significantly changed by star scattering and the cluster potential
before XZKL occurs in the planets' orbits. Across different cluster models,
0.8\%-3\% of the planets orbiting initially-single stars have experienced XZKL
while the fraction is 2\%-26\% for initially-binary stars. Notably, the
ejection fraction is similar to or appreciably smaller than XZKL. Around a star
that is binary at 1 Gyr, 13\%-32\% of its planets have undergone XZKL, and
combined with single stars, the overall XZKL fraction is 3\%-21\%, most
affected by the cluster binarity. If 10\% of the stars in M67 host a giant
planet, our model predicts an HJ occurrence rate of . We suggest that
HJ surveys target old, high-binarity, not-too-dense open clusters and
prioritise wide binaries to maximise HJ yield.Comment: 12 figures, 2 tables, submitted to MNRA
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