1,075 research outputs found

### The small and large lags of the elastic and anelastic tides. The virtual identity of two rheophysical theories

The aim of this letter is to discuss the virtual identity of two recent tidal
theories: the creep tide theory of Ferraz-Mello (Cel. Mech. Dyn. Astron. 116,
109, 2013) and the Maxwell model developed by Correia et al. (Astron.
Astrophys. 571, A50, 2014). It includes the discussion of the basic equations
of the theories, which, in both cases, include an elastic and an anelastic
component, and shows that the basic equations of the two theories are
equivalent and differ by only a numerical factor in the anelastic tide. It also
includes a discussion of the lags: the lag of the full tide (geodetic),
dominated by the elastic component, and the phase of the anelastic tide. In
rotating rocky bodies not trapped in a spin-orbit resonance (e.g., the Earth)
the geodetic lag is close to zero and the phase of the semi-diurnal argument in
the anelastic tide is close to 90 degrees. The results obtained from combining
tidal solutions from satellite tracking data and from Topex/Poseidon satellite
altimeter data, by Ray et al., are extended to determine the phase of the
semi-diurnal argument in the Earth's anelastic tide as sigma_0=89.80 \pm 0.05
degrees.Comment: Accepted for publication in Astronomy and Astrophysic

### On planetary mass determination in the case of super-Earths orbiting active stars. The case of the CoRoT-7 system

This investigation uses the excellent HARPS radial velocity measurements of
CoRoT-7 to re-determine the planet masses and to explore techniques able to
determine mass and elements of planets discovered around active stars when the
relative variation of the radial velocity due to the star activity cannot be
considered as just noise and can exceed the variation due to the planets. The
main technique used here is a self-consistent version of the high-pass filter
used by Queloz et al. (2009) in the first mass determination of CoRoT-7b and
CoRoT-7c. The results are compared to those given by two alternative
techniques: (1) The approach proposed by Hatzes et al. (2010) using only those
nights in which 2 or 3 observations were done; (2) A pure Fourier analysis. In
all cases, the eccentricities are taken equal to zero as indicated by the study
of the tidal evolution of the system; the periods are also kept fixed at the
values given by Queloz et al. Only the observations done in the time interval
BJD 2,454,847 - 873 are used because they include many nights with multiple
observations; otherwise it is not possible to separate the effects of the
rotation fourth harmonic (5.91d = Prot/4) from the alias of the orbital period
of CoRoT-7b (0.853585 d). The results of the various approaches are combined to
give for the planet masses the values 8.0 \pm 1.2 MEarth for CoRoT-7b and 13.6
\pm 1.4 MEarth for CoRoT 7c. An estimation of the variation of the radial
velocity of the star due to its activity is also given.The results obtained
with 3 different approaches agree to give masses larger than those in previous
determinations. From the existing internal structure models they indicate that
CoRoT-7b is a much denser super-Earth. The bulk density is 11 \pm 3.5 g.cm-3 .
CoRoT-7b may be rocky with a large iron core.Comment: 12 pages, 11 figure

### Extrasolar Planets in Mean-Motion Resonance: Apses Alignment and Asymmetric Stationary Solutions

In recent years several pairs of extrasolar planets have been discovered in
the vicinity of mean-motion commensurabilities. In some cases, such as the
Gliese 876 system, the planets seem to be trapped in a stationary solution, the
system exhibiting a simultaneous libration of the resonant angle theta_1 = 2
lambda_2 - lambda_1 - varpi_1 and of the relative position of the pericenters.
In this paper we analyze the existence and location of these stable
solutions, for the 2/1 and 3/1 resonances, as function of the masses and
orbital elements of both planets. This is undertaken via an analytical model
for the resonant Hamiltonian function. The results are compared with those of
numerical simulations of the exact equations.
In the 2/1 commensurability, we show the existence of three principal
families of stationary solutions: (i) aligned orbits, in which theta_1 and
varpi_1 - varpi_2 both librate around zero, (ii) anti-aligned orbits, in which
theta_1=0 and the difference in pericenter is 180 degrees, and (iii) asymmetric
stationary solutions, where both the resonant angle and varpi_1 - varpi_2 are
constants with values different of 0 or 180 degrees. Each family exists in a
different domain of values of the mass ratio and eccentricities of both
planets. Similar results are also found in the 3/1 resonance.
We discuss the application of these results to the extrasolar planetary
systems and develop a chart of possible planetary orbits with apsidal
corotation. We estimate, also, the maximum planetary masses in order that the
stationary solutions are dynamically stable.Comment: 25 pages, 10 figures. Submitted to Ap

### III.9-2 Tidal evolution of CoRoT massive planets and brown dwarfs and of their host stars

This book is dedicated to all the people interested in the CoRoT mission and the beautiful data that were delivered during its six year duration. Either amateurs, professional, young or senior researchers, they will find treasures not only at the time of this publication but also in the future twenty or thirty years. It presents the data in their final version, explains how they have been obtained, how to handle them, describes the tools necessary to understand them, and where to find them. It also highlights the most striking first results obtained up to now. CoRoT has opened several unexpected directions of research and certainly new ones still to be discovered

### On Tides and Exoplanets

This paper reviews the basic equations used in the study of the tidal
variations of the rotational and orbital elements of a system formed by one
star and one close-in planet as given by the creep tide theory and Darwin's
constant time lag (CTL) theory. At the end, it reviews and discusses the
determinations of the relaxation factors (and time lags) in the case of host
stars and hot Jupiters based on actual observations of orbital decay, stellar
rotation and age, etc. It also includes a recollection of the basic facts
concerning the variations of the rotation of host stars due to the leakage of
angular momentum associated with stellar winds.Comment: 4 figures, IAU Symposium No. 36

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