We consider the full Solar System including(1) Ceres and some of the main asteroids, (2) Pallas, (4) Vesta, (7) Iris, and (324) Bamberga. We show that close encounters amongthese small bodies induce ...strong chaotic behavior in their orbits and in those of many asteroids that are much more chaotic than previously thought. Even if space missions will allow very precise measurements of the positions of Ceres and Vesta, their motion will be unpredictable over 400 kyr. As a result, it will never be possible to recover the precise evolution of the Earth’s eccentricity beyond 60 Myr. Ceres and Vesta thus appear to be the main limiting factors for any precise reconstruction of the Earth orbit, which is fundamental for the astronomical calibration of geological timescales. Moreover, collisions of Ceres and Vesta are possible, with a collision probability of 0.2% per Gyr.
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We report the discovery of four super-Earth planets around HD 215152, with orbital periods of 5.76, 7.28, 10.86, and 25.2 d, and minimum masses of 1.8, 1.7, 2.8, and 2.9
M
⊕
respectively. This ...discovery is based on 373 high-quality radial velocity measurements taken by HARPS over 13 yr. Given the low masses of the planets, the signal-to-noise ratio is not sufficient to constrain the planet eccentricities. However, a preliminary dynamical analysis suggests that eccentricities should be typically lower than about 0.03 for the system to remain stable. With two pairs of planets with a period ratio lower than 1.5, with short orbital periods, low masses, and low eccentricities, HD 215152 is similar to the very compact multi-planet systems found by
Kepler
, which is very rare in radial-velocity surveys. This discovery proves that these systems can be reached with the radial-velocity technique, but characterizing them requires a huge amount of observations.
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Context.
Since 1998, a planet-search around main sequence stars within 50 pc in the southern hemisphere has been underway with the CORALIE spectrograph at La Silla Observatory.
Aims.
With an ...observing time span of more than 20 yr, the CORALIE survey is able to detect long-term trends in data with masses and separations large enough to select ideal targets for direct imaging. Detecting these giant companion candidates will allow us to start bridging the gap between radial-velocity-detected exoplanets and directly imaged planets and brown dwarfs.
Methods.
Long-term precise Doppler measurements with the CORALIE spectrograph reveal radial-velocity signatures of massive planetary companions and brown dwarfs on long-period orbits.
Results.
In this paper, we report the discovery of new companions orbiting HD 181234, HD 13724, HD 25015, HD 92987 and HD 50499. We also report updated orbital parameters for HD 50499b, HD 92788b and HD 98649b. In addition, we confirm the recent detection of HD 92788c. The newly reported companions span a period range of 15.6–40.4 yr and a mass domain of 2.93–26.77
M
Jup
, the latter of which straddles the nominal boundary between planets and brown dwarfs.
Conclusions.
We report the detection of five new companions and updated parameters of four known extrasolar planets. We identify at least some of these companions to be promising candidates for imaging and further characterisation.
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ABSTRACT
Eccentricity is a parameter of particular interest as it is an informative indicator of the past of planetary systems. It is however not always clear whether the eccentricity fitted on ...radial velocity data is real or if it is an artefact of an inappropriate modelling. In this work, we address this question in two steps: we first assume that the model used for inference is correct and present interesting features of classical estimators. Secondly, we study whether the eccentricity estimates are to be trusted when the data contain incorrectly modelled signals, such as missed planetary companions, non-Gaussian noises, correlated noises with unknown covariance, etc. Our main conclusion is that data analysis via posterior distributions, with a model including a free error term gives reliable results provided two conditions. First, convergence of the numerical methods needs to be ascertained. Secondly, the noise power spectrum should not have a particularly strong peak at the semiperiod of the planet of interest. As a consequence, it is difficult to determine if the signal of an apparently eccentric planet might be due to another inner companion in 2:1 mean motion resonance. We study the use of Bayes factors to disentangle these cases. Finally, we suggest methods to check if there are hints of an incorrect model in the residuals. We show on simulated data the performance of our methods and comment on the eccentricities of Proxima b and 55 Cnc f.
Multiplanetary systems detected by the Kepler mission present an excess of planets close to first-order mean-motion resonances (2:1 and 3:2), but with a period ratio slightly higher than the resonant ...value. Several mechanisms have been proposed to explain this observation. Here we provide some clues that indicate that these near-resonant systems were initially in resonance and reached their current configuration through tidal dissipation. It has been argued that this only applies to the close-in systems and not to the farthest ones, for which the tidal effect is too weak. Using the KOI catalog of the Kepler mission, we show that the distributions of the period ratio among the most close-in and the farthest planetary systems differ significantly. This distance-dependent repartition is a strong argument in favor of the tidal dissipation scenario.
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Transit timing variations (TTVs) can provide useful information for systems observed by transit, as they allow us to put constraints on the masses and eccentricities of the observed planets, or even ...to constrain the existence of non-transiting companions. However, TTVs can also act as a detection bias that can prevent the detection of small planets in transit surveys that would otherwise be detected by standard algorithms such as the Boxed Least Square algorithm if their orbit was not perturbed. This bias is especially present for surveys with a long baseline, such as
Kepler
, some of the TESS sectors, and the upcoming PLATO mission. Here we introduce a detection method that is robust to large TTVs, and illustrate its use by recovering and confirming a pair of resonant super-Earths with ten-hour TTVs around Kepler-1705 (prev. KOI-4772). The method is based on a neural network trained to recover the tracks of low-signal-to-noise-ratio (S/N) perturbed planets in river diagrams. We recover the transit parameters of these candidates by fitting the light curve. The individual transit S/N of Kepler-1705b and c are about three times lower than all the previously known planets with TTVs of 3 h or more, pushing the boundaries in the recovery of these small, dynamically active planets. Recovering this type of object is essential for obtaining a complete picture of the observed planetary systems, and solving for a bias not often taken into account in statistical studies of exoplanet populations. In addition, TTVs are a means of obtaining mass estimates which can be essential for studying the internal structure of planets discovered by transit surveys. Finally, we show that due to the strong orbital perturbations, it is possible that the spin of the outer resonant planet of Kepler-1705 is trapped in a sub- or super-synchronous spin–orbit resonance. This would have important consequences for the climate of the planet because a non-synchronous spin implies that the flux of the star is spread over the whole planetary surface.
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Context.
S-type planets, which orbit one component of multiple-star systems, place strong constraints on planet formation and evolution models. A notable case study is Kepler-444, a triple-star ...system whose primary is orbited by five planets smaller than Venus in a compact configuration, and for which the stellar binary companion revolves around the primary on a highly eccentric orbit.
Aims.
Several open questions remain about the formation and evolution of Kepler-444. Having access to the most precise up-to-date masses and orbital parameters is highly valuable when tackling those questions. We provide the first full dynamical exploration of this system, with the goal being to refine those parameters.
Methods.
We apply orbital stability arguments to refine the system parameters on models with and without the stellar binary companion in order to understand the origin of the dynamical constraints. This approach makes use of the numerical analysis of fundamental frequencies fast chaos indicator. We also explore potential two- and three-planet mean-motion resonances (MMRs) in the system. Prior to investigating the dynamics of a model that includes the binary companion, we update its orbital parameters and mass using new observational constraints from both HIRES radial velocity and
Gaia
astrometric data, as well as archival imaging of the system.
Results.
The planetary system does not appear in any of the low-order two- or three-planet MMRs. We provide the most precise up-to-date dynamical parameters for the planets and the stellar binary companion. The orbit of the latter is constrained by the new observations, and also by the stability analysis. This update further challenges the planets formation processes. We also test the dynamical plausibility of a sixth planet in the system, following hints found in HST data. We find that this putative planet could exist over a broad range of masses, and with an orbital period of between roughly 12 and 20 days.
Conclusions.
We note the overall good agreement of the system with short-term orbital stability. This suggests that a diverse range of planetary system architectures could be found in multiple-star systems, potentially challenging the planet formation models further.
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Transit timing variations (TTVs) can provide useful information on compact multi-planetary systems observed by transits by setting constraints on the masses and eccentricities of the observed ...planets. This is especially helpful when the host star is not bright enough for a radial velocity (RV) follow-up. However, in the past decade, a number of works have shown that TTV-characterised planets tend to have lower densities than planets characterised on the basis of RVs. Re-analysing 34
Kepler
planets in the super-Earth to sub-Neptunes range using the RIVERS approach, we show that at least some of these discrepancies were due to the way transit timings were extracted from the light curve, as a result of their tendency to underestimate the TTV amplitudes. We recovered robust mass estimates (i.e. with low prior dependency) for 23 of the planets. We compared these planets the RV-characterised population and found that a large fraction of those that previously had unusually low density estimates were adjusted, allowing them to occupy a place on the mass-radius diagram much closer to the bulk of known planets. However, a slight shift toward lower densities remains, which could indicate that the compact multi-planetary systems characterised by TTVs are indeed composed of planets that are different from the bulk of the RV-characterised population. These results are especially important in the context of obtaining an unbiased view of the compact multi-planetary systems detected by
Kepler
, TESS, and the upcoming PLATO mission.
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In October 2014, an outbreak of 12 autochthonous chikungunya cases, 11 confirmed and 1 probable, was detected in a district of Montpellier, a town in the south of France colonised by the vector Aedes ...albopictus since 2010. A case returning from Cameroon living in the affected district was identified as the primary case. The epidemiological investigations and the repeated vector control treatments performed in the area and around places frequented by cases helped to contain the outbreak. In 2014, the chikungunya and dengue surveillance system in mainland France was challenged by numerous imported cases due to the chikungunya epidemic ongoing in the Caribbean Islands. This first significant outbreak of chikungunya in Europe since the 2007 Italian epidemic, however, was due to an East Central South African (ECSA) strain, imported by a traveller returning from West Africa. Important lessons were learned from this episode, which reminds us that the threat of a chikungunya epidemic in southern Europe is real.
Context.
Over recent years, the number of detected multi-planet systems has grown significantly. An important subclass of these are the compact configurations. Precise knowledge of this subclass is ...crucial for understanding the conditions in which planetary systems form and evolve. However, observations often leave these systems with large uncertainties, notably on the orbital eccentricities. This is especially prominent for systems with low-mass planets detected with radial velocities, and increasing numbers of these are being discovered in the exoplanet population. Refining these parameters with the help of orbital stability arguments is becoming a common approach.
Aims.
Such dynamical techniques can be computationally expensive. In this work, we use an alternative procedure that is orders of magnitude faster than classical N-body integration approaches, and has the potential to narrow down parameter uncertainties.
Methods.
We coupled a reliable exploration of the parameter space with the precision of the Numerical Analysis of Fundamental Frequencies (Laskar, J. 1990, Icarus, 88, 266) fast chaos indicator. We also propose a general procedure to calibrate the NAFF indicator on any multi-planet system without additional computational cost. This calibration strategy is illustrated using the compact multiplanet system HD 45364, in addition to yet-unpublished measurements obtained with the HARPS and CORALIE high-resolution spectrographs. We validate the calibration approach by a comparison with long integrations performed on HD 202696. We test the performances of this stability-driven approach on two systems with different architectures: first we study HD 37124, a three-planet system composed of planets in the Jovian regime; then, we analyse the stability constraints on HD 215152, a compact system of four low-mass planets.
Results.
We revise the planetary parameters for HD 45364, HD 202696, HD 37124, and HD 215152, and provide a comprehensive view of the dynamical state these systems are in.
Conclusions.
We demonstrate the potential of the NAFF stability-driven approach to refine the orbital parameters and planetary masses. We stress the importance of undertaking systematic global dynamical analyses on every new multi-planet system discovered.
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