13,866 research outputs found
HD60532, a planetary system in a 3:1 mean motion resonance
In a recent paper it was reported a planetary system around the star HD60532,
composed by two giant planets in a possible 3:1 mean motion resonance, that
should be confirmed within the next decade. Here we show that the analysis of
the global dynamics of the system allows to confirm this resonance. The present
best fit to data already corresponds to this resonant configuration and the
system is stable for at least 5Gry. The 3:1 resonance is so robust that
stability is still possible for a wide variety of orbital parameters around the
best fit solution and also if the inclination of the system orbital plane with
respect to the plane of the sky is as small as 15 deg. Moreover, if the
inclination is taken as a free parameter in the adjustment to the observations,
we find an inclination ~ 20 deg, which corresponds to M_b =3.1 M_Jup and M_c =
7.4 M_Jup for the planetary companions.Comment: 4 Pages, 4 Figures, accepted by A&
Anisotropic simplicial minisuperspace model
The computation of the simplicial minisuperspace wavefunction in the case of
anisotropic universes with a scalar matter field predicts the existence of a
large classical Lorentzian universe like our own at late timesComment: 19 pages, Latex, 6 figure
On the equilibrium rotation of Earth-like extra-solar planets
The equilibrium rotation of tidally evolved "Earth-like" extra-solar planets
is often assumed to be synchronous with their orbital mean motion. The same
assumption persisted for Mercury and Venus until radar observations revealed
their true spin rates. As many of these planets follow eccentric orbits and are
believed to host dense atmospheres, we expect the equilibrium rotation to
differ from the synchronous motion. Here we provide a general description of
the allowed final equilibrium rotation states of these planets, and apply this
to already discovered cases in which the mass is lower than twelve
Earth-masses. At low obliquity and moderate eccentricity, it is shown that
there are at most four distinct equilibrium possibilities, one of which can be
retrograde. Because most presently known "Earth-like" planets present eccentric
orbits, their equilibrium rotation is unlikely to be synchronous.Comment: 4 pages, 2 figures. accepted for publication in Astronomy and
Astrophysics. to be published in Astronomy and Astrophysic
Resonance breaking due to dissipation in planar planetary systems
We study the evolution of two planets around a star, in mean-motion resonance
and undergoing tidal effect. We derive an integrable analytical model of
mean-motion resonances of any order which reproduce the main features of the
resonant dynamics. Using this simplified model, we obtain a criterion showing
that depending on the balance of the tidal dissipation in both planets, their
final period ratio may stay at the resonant value, increase above, or decrease
below the resonant value.
Applying this criterion to the two inner planets orbiting GJ163, we deduce
that the current period ratio (2.97) could be the outcome of dissipation in the
3:1 MMR provided that the innermost planet is gaseous (slow dissipation) while
the second one is rocky (faster dissipation). We perform N-body simulations
with tidal dissipation to confirm the results of our analytical model.
We also apply our criterion on GJ581b, c (5:2 MMR) and reproduce the current
period ratio (2.4) if the inner planet is gaseous and the outer is rocky (as
for GJ163).
Finally, we apply our model to the Kepler mission's statistics. We show that
the excess of planets pairs close to first order MMR but in external
circulation, i.e., with period ratios P_out/P_in > (p+1)/p for the resonance
(p+1):p, can be reproduced by tidal dissipation in the inner planet. There is
no need for any other dissipative mechanism, provided that these systems left
the resonance with non-negligible eccentricities.Comment: 14 pages, 9 figures, submitted for publicatio
Dynamical stability analysis of the HD202206 system and constraints to the planetary orbits
Long-term precise Doppler measurements with the CORALIE spectrograph revealed
the presence of two massive companions to the solar-type star HD202206.
Although the three-body fit of the system is unstable, it was shown that a 5:1
mean motion resonance exists close to the best fit, where the system is stable.
We present here an extensive dynamical study of the HD202206 system aiming at
constraining the inclinations of the two known companions, from which we derive
possible ranges of value for the companion masses.
We study the long term stability of the system in a small neighborhood of the
best fit using Laskar's frequency map analysis. We also introduce a numerical
method based on frequency analysis to determine the center of libration mode
inside a mean motion resonance.
We find that acceptable coplanar configurations are limited to inclinations
to the line of sight between 30 and 90 degrees. This limits the masses of both
companions to roughly twice the minimum. Non coplanar configurations are
possible for a wide range of mutual inclinations from 0 to 90 degrees, although
configurations seem to be favored. We also confirm the
5:1 mean motion resonance to be most likely. In the coplanar edge-on case, we
provide a very good stable solution in the resonance, whose does not
differ significantly from the best fit. Using our method to determine the
center of libration, we further refine this solution to obtain an orbit with a
very low amplitude of libration, as we expect dissipative effects to have
dampened the libration.Comment: 14 pages, 18 figure
Influence of labyrinth orientation relative to gravity on responses elicited by stimulation of the horizontal semicircular canals
Gravity labyrinth orientation influence on responses from stimulation of horizontal semicircular canal
Modification of vestibular responses as a function of rate of rotation about an earth-horizontal axis
Vestibular response modifications as function of rotation rate about earth-horizontal axi
Kinematics nomenclature for physiological accelerations with special reference to vestibular applications
Kinematics nomenclature for physiological accelerations and special reference to vestibular apparatu
Tidal damping of the mutual inclination in hierachical systems
Hierarchical two-planet systems, in which the inner body's semi-major axis is
between 0.1 and 0.5 AU, usually present high eccentricity values, at least for
one of the orbits. As a result of the formation process, one may expect that
planetary systems with high eccentricities also have high mutual inclinations.
However, here we show that tidal effects combined with gravitational
interactions damp the initial mutual inclination to modest values in timescales
that are shorter than the age of the system. This effect is not a direct
consequence of tides on the orbits, but it results from a secular forcing of
the inner planet's flattening. We then conclude that these hierarchical
planetary systems are unlikely to present very high mutual inclinations, at
least as long as the orbits remain outside the Lidov-Kozai libration areas. The
present study can also be extended to systems of binary stars and to
planet-satellite systems.Comment: 16 pages, 13 figure
Elicitation of horizontal nystagmus by periodic linear acceleration
Horizontal nystagmus elicitation in man by periodic linear acceleratio
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