412 research outputs found
AMD-stability in presence of first order Mean Motion Resonances
The AMD-stability criterion allows to discriminate between a-priori stable
planetary systems and systems for which the stability is not granted and needs
further investigations. AMD-stability is based on the conservation of the
Angular Momentum Deficit (AMD) in the averaged system at all orders of
averaging. While the AMD criterion is rigorous, the conservation of the AMD is
only granted in absence of mean-motion resonances (MMR). Here we extend the
AMD-stability criterion to take into account mean-motion resonances, and more
specifically the overlap of first order MMR. If the MMR islands overlap, the
system will experience generalized chaos leading to instability. The
Hamiltonian of two massive planets on coplanar quasi-circular orbits can be
reduced to an integrable one degree of freedom problem for period ratios close
to a first order MMR. We use the reduced Hamiltonian to derive a new overlap
criterion for first order MMR. This stability criterion unifies the previous
criteria proposed in the literature and admits the criteria obtained for
initially circular and eccentric orbits as limit cases. We then improve the
definition of AMD-stability to take into account the short term chaos generated
by MMR overlap. We analyze the outcome of this improved definition of
AMD-stability on selected multi-planet systems from the Extrasolar Planets
Encyclopeadia.Comment: Accepted by A and A 07/10/1
Impact of stellar companions on precise radial velocities
Context: With the announced arrival of instruments such as ESPRESSO one can
expect that several systematic noise sources on the measurement of precise
radial velocity will become the limiting factor instead of photon noise. A
stellar companion within the fiber is such a possible noise source. Aims: With
this work we aim at characterizing the impact of a stellar companion within the
fiber to radial velocity measurements made by fiber-fed spectrographs. We
consider the contaminant star either to be part of a binary system whose
primary star is the target star, or as a background/foreground star. Methods:
To carry out our study, we used HARPS spectra, co-added the target with
contaminant spectra, and then compared the resulting radial velocity with that
obtained from the original target spectrum. We repeated this procedure and used
different tunable knobs to reproduce the previously mentioned scenarios.
Results: We find that the impact on the radial velocity calculation is a
function of the difference between individual radial velocities, of the
difference between target and contaminant magnitude, and also of their spectral
types. For the worst-case scenario in which both target and contaminant star
are well centered on the fiber, the maximum contamination for a G or K star may
be higher than 10 cm/s, on average, if the difference between target and
contaminant magnitude is < 10, and higher than 1 m/s if <
8. If the target star is of spectral type M, < 8 produces the same
contamination of 10 cm/s, and a contamination may be higher than 1 m/sComment: Accepted for publication in A&A on 29/12/2019 - 14 page
Deformation and tidal evolution of close-in planets and satellites using a Maxwell viscoelastic rheology
In this paper we present a new approach to tidal theory. Assuming a Maxwell
viscoelastic rheology, we compute the instantaneous deformation of celestial
bodies using a differential equation for the gravity field coefficients. This
method allows large eccentricities and it is not limited to quasi-periodic
perturbations. It can take into account an extended class of perturbations,
including chaotic motions and transient events. We apply our model to some
already detected eccentric hot Jupiters and super-Earths in planar
configurations. We show that when the relaxation time of the deformation is
larger than the orbital period, spin-orbit equilibria arise naturally at
half-integers of the mean motion, even for gaseous planets. In the case of
super-Earths, these equilibria can be maintained for very low values of
eccentricity. Our method can also be used to study planets with complex
internal structures and other rheologies.Comment: 16 pages, 13 figures, 2 table
Probing the effect of gravitational microlensing on the measurements of the Rossiter-McLaughlin effect
In general, in the studies of transit light-curves and the
Rossiter-McLaughlin (RM), the contribution of the planet's gravitational
microlensing is neglected. Theoretical studies, have, however shown that the
planet's microlensing can affect the transit light-curve and in some extreme
cases cause the transit depth to vanish. In this letter, we present the results
of our quantitative analysis of microlening on the RM effect. Results indicate
that for massive planets in on long period orbits, the planet's microlensing
will have considerable contribution to the star's RV measurements. We present
the details of our study, and discuss our analysis and results.Comment: 6 pages, 3 figures, accepted for publication in Astronomy &
Astrophysic
Improvements on analytic modelling of stellar spots
In this work we present the solution of the stellar spot problem using the
Kelvin-Stokes theorem. Our result is applicable for any given location and
dimension of the spots on the stellar surface. We present explicitely the
result up to the second degree in the limb darkening law. This technique can be
used to calculate very efficiently mutual photometric effects produced by
eclipsing bodies occulting stellar spots and to construct complex spot shapes.Comment: Resubmitted to MNRAS after accounting for minor comments of second
review, 9 pages, 5 figures, software available at
http://eduscisoft.com/KSINT
SOAP-T: A tool to study the light-curve and radial velocity of a system with a transiting planet and a rotating spotted star
We present an improved version of SOAP (Boisse et al. 2012) named "SOAP-T",
which can generate the radial velocity variations and light-curves for systems
consisting of a rotating spotted star with a transiting planet. This tool can
be used to study the anomalies inside transit light-curves and the
Rossiter-McLaughlin effect, to better constrain the orbital configuration and
properties of planetary systems and active zones of their host stars. Tests of
the code are presented to illustrate its performance and to validate its
capability when compared with analytical models and real data. Finally, we
apply SOAP-T to the active star, HAT-P-11, observed by the NASA Kepler space
telescope and use this system to discuss the capability of this tool in
analyzing light-curves for the cases where the transiting planet overlaps with
the star's spots.Comment: 9 pages, 7 figures, accepted for publication in Astronomy and
Astrophysic
ââLozengeââ contour plots in scattering from polymer networks
We present a consistent explanation for the appearance of âlozengeâ shapes in contour plots of the two dimensional scattering intensity from stretched polymer networks. By explicitly averaging over quenched variables in a tube model, we show that lozenge patterns arise as a result of chain material that is not directly deformed by the stretch. We obtain excellent agreement with experimental data
Polarization of thick polyvinylidene fluoride/trifluoroethylene copolymer films
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