445 research outputs found
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 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
Tidal Evolution of Close-in Exoplanets and Host Stars
The evolution of exoplanetary systems with a close-in planet is ruled by the
tides mutually raised on the two bodies and by the magnetic braking of the host
star. This paper deals with consequences of this evolution and some features
that can be observed in the distribution of the systems two main periods: the
orbital periods and the stars rotational periods. The results of the
simulations are compared to plots showing both periods as determined from the
light curves of a large number of Kepler objects of interest. These plots show
important irregularities as a dearth of systems in some regions and
accumulations of hot Jupiters in others. It is shown that the accumulation of
short-period hot Jupiters around stars with rotation periods close to 25 days
results from the evolution of the systems under the joint action of tides and
braking, and requires a relaxation factor for solar-type stars of around .Comment: Accepted for publication in MNRA
Dynamics of Enceladus and Dione inside the 2:1 Mean-Motion Resonance under Tidal Dissipation
In a previous work (Callegari and Yokoyama 2007, Celest. Mech. Dyn. Astr.
vol. 98), the main features of the motion of the pair Enceladus-Dione were
analyzed in the frozen regime, i.e., without considering the tidal evolution.
Here, the results of a great deal of numerical simulations of a pair of
satellites similar to Enceladus and Dione crossing the 2:1 mean-motion
resonance are shown. The resonance crossing is modeled with a linear tidal
theory, considering a two-degrees-of-freedom model written in the framework of
the general three-body planar problem. The main regimes of motion of the system
during the passage through resonance are studied in detail. We discuss our
results comparing them with classical scenarios of tidal evolution of the
system. We show new scenarios of evolution of the Enceladus-Dione system
through resonance not shown in previous approaches of the problem.Comment: 36 pages, 12 figures. Accepted in Celestial Mechanics and Dynamical
Astronom
Tidal decay and circularization of the orbits of short-period planets
We analyze the long-term tidal evolution of a single-planet system through
the use of numerical simulations and averaged equations giving the variations
of semi-major axis and eccentricity of the relative orbit. For different types
of planets, we compute the variations due to the planetary and stellar tides.
Then, we calculate the critical value of the eccentricity for which the stellar
tide becomes dominant over the planetary tide. The timescales for orbital decay
and circularization are also discussed and compared.Comment: 8 pages, 3 figures, corrected typo
A new analysis of the GJ581 extrasolar planetary system
We have done a new analysis of the available observations for the GJ581
exoplanetary system. Today this system is controversial due to choices that can
be done in the orbital determination. The main ones are the ocurrence of
aliases and the additional bodies - the planets f and g - announced in Vogt et
al. 2010. Any dynamical study of exoplanets requires the good knowledge of the
orbital elements and the investigations involving the planet g are particularly
interesting, since this body would lie in the Habitable Zone (HZ) of the star
GJ581. This region,for this system, is very attractive of the dynamical point
of view due to several resonances of two and three bodies present there. In
this work, we investigate the conditions under which the planet g may exist. We
stress the fact that the planet g is intimately related with the orbital
elements of the planet d; more precisely, we conclude that it is not possible
to disconnect its existence from the determination of the eccentricity of the
planet d. Concerning the planet f, we have found one solution with period
days, but we are judicious about any affirmation concernig this
body because its signal is in the threshold of detection and the high period is
in a spectral region where the ocorruence of aliases is very common. Besides,
we outline some dynamical features of the habitable zone with the dynamical map
and point out the role played by some resonances laying there.Comment: 12 pages, 9 figure
III.9 Star-planet Interactions
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
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