CoRoT pictures transiting exoplanets

The detection and characterization of exoplanets have made huge progresses since the first discoveries in the late nineties. In particular, the independent measurement of the mass and radius of planets, by combining the transit and radial-velociy techniques, allowed exploring their density and hence, their internal structure. With CoRoT (2007-2012), the pioneering CNES space-based mission in this investigation, about thirty new planets were characterized. CoRoT has enhanced the diversity of giant exoplanets and discovered the first telluric exoplanet. Following CoRoT, the NASA Kepler mission has extended our knowledge to small-size planets, multiple systems and planets orbiting binaries. Exploring these new worlds will continue with the NASA/TESS (2017) and ESA/PLATO (2024) missions.Comment: in Comptes Rendus de l'Academie des Sciences / Geoscienc

An upper boundary in the mass-metallicity plane of exo-Neptunes

With the progress of detection techniques, the number of low-mass and small-size exoplanets is increasing rapidly. However their characteristics and formation mechanisms are not yet fully understood. The metallicity of the host star is a critical parameter in such processes and can impact the occurence rate or physical properties of these planets. While a frequency-metallicity correlation has been found for giant planets, this is still an ongoing debate for their smaller counterparts. Using the published parameters of a sample of 157 exoplanets lighter than 40 Mearth, we explore the mass-metallicity space of Neptunes and Super-Earths. We show the existence of a maximal mass that increases with metallicity, that also depends on the period of these planets. This seems to favor in situ formation or alternatively a metallicity-driven migration mechanism. It also suggests that the frequency of Neptunes (between 10 and 40 Mearth) is, like giant planets, correlated with the host star metallicity, whereas no correlation is found for Super-Earths (<10 Mearth).Comment: Accepted in MNRAS, 11 pages, 5 figure

New planetary and EB candidates from Campaigns 1-6 of the K2 mission

With only two functional reaction wheels, Kepler cannot maintain stable pointing at its original target field and entered a new mode of observation called K2. Our method is based on many years of experience in planet hunting for the CoRoT mission. Due to the unstable pointing, K2 light curves present systematics that are correlated with the target position in the CCD. Therefore, our pipeline also includes a decorrelation of this systematic noise. Our pipeline is optimised for bright stars for which spectroscopic follow-up is possible. We achieve a maximum precision on 6 hours of 6 ppm. The decorrelated light curves are searched for transits with an adapted version of the CoRoT alarm pipeline. We present 172 planetary candidates and 327 eclipsing binary candidates from campaigns 1, 2, 3, 4, 5 and 6 of K2. Both the planetary candidates and eclipsing binary candidates lists are made public to promote follow-up studies. The light curves will also be available to the community.Comment: 22 pages. 5 figures, 4 tables, Accepted for publication in A&

Introduction

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

The CoRoT Exoplanet program : status & results

The CoRoT satellite is the first instrument hunting for planets from space. We will review the status of the CoRoT/Exoplanet program. We will then present the CoRoT exoplanetary systems and how they widen the range of properties of the close-in population and contribute to our understanding of the properties of planets.Comment: 10 pages, Proceeding of Haute Provence Observatory Colloquium (23-27 August 2010

High-resolution infrared spectroscopy as a tool to detect false positives of transit search programs

Transit search programs such as CoRoT and Kepler now have the capability of detecting planets as small as the Earth. The detection of these planets however requires the removal of all false positives. Although many false positives can be identified by a detailed analysis of the LCs, the detections of others require additional observations. An important source of false positives are faint eclipsing binaries within the PSF of the target stars. We develop a new method that allows us to detect faint eclipsing binaries with a separation smaller than one arcsec from target stars. We thereby focus on binaries that mimic the transits of terrestrial planets. These binaries can be either at the same distance as the target star (triple stars), or at either larger, or smaller distances. A close inspection of the problem indicates that in all relevant cases the binaries are brighter in the infrared than in the optical regime. We show how high resolution IR spectroscopy can be used to remove these false positives. For the triple star case, we find that the brightness difference between a primary and an eclipsing secondary is about 9-10 mag in the visual but only about 4.5-5.9 magnitudes in the K-band. We demonstrate how the triple star hypothesis can be excluded by taking a high-resolution IR spectrum. Simulations of these systems show that the companions can be detected with a false-alarm probability of 2%, if the spectrum has a S/N-ratio > 100. We show that high-resolution IR spectra also allows to detect most of the false positives caused by foreground or background binaries. If high resolution IR spectroscopy is combined with photometric methods, virtually all false positives can be detected without RV measurements. It is thus possible to confirm transiting terrestrial planets with a modest investment of observing time.Comment: 6 pages, 7 figure

PASTIS: Bayesian extrasolar planet validation. I. General framework, models, and performance

A large fraction of the smallest transiting planet candidates discovered by the Kepler and CoRoT space missions cannot be confirmed by a dynamical measurement of the mass using currently available observing facilities. To establish their planetary nature, the concept of planet validation has been advanced. This technique compares the probability of the planetary hypothesis against that of all reasonably conceivable alternative false-positive (FP) hypotheses. The candidate is considered as validated if the posterior probability of the planetary hypothesis is sufficiently larger than the sum of the probabilities of all FP scenarios. In this paper, we present PASTIS, the Planet Analysis and Small Transit Investigation Software, a tool designed to perform a rigorous model comparison of the hypotheses involved in the problem of planet validation, and to fully exploit the information available in the candidate light curves. PASTIS self-consistently models the transit light curves and follow-up observations. Its object-oriented structure offers a large flexibility for defining the scenarios to be compared. The performance is explored using artificial transit light curves of planets and FPs with a realistic error distribution obtained from a Kepler light curve. We find that data support for the correct hypothesis is strong only when the signal is high enough (transit signal-to-noise ratio above 50 for the planet case) and remains inconclusive otherwise. PLATO shall provide transits with high enough signal-to-noise ratio, but to establish the true nature of the vast majority of Kepler and CoRoT transit candidates additional data or strong reliance on hypotheses priors is needed.Comment: Accepted for publication in MNRAS; 23 pages, 11 figure

Stellar Limb-Darkening Coefficients for CoRot and Kepler

Transiting exoplanets provide unparalleled access to the fundamental parameters of both extrasolar planets and their host stars. We present limb-darkening coefficients (LDCs) for the exoplanet hunting CoRot and Kepler missions. The LDCs are calculated with ATLAS stellar atmospheric model grids and span a wide range of Teff, log g, and metallically [M/H]. Both CoRot and Kepler contain wide, nonstandard response functions, and are producing a large inventory of high-quality transiting lightcurves, sensitive to stellar limb darkening. Comparing the stellar model limb darkening to results from the first seven CoRot planets, we find better fits are found when two model intensities at the limb are excluded in the coefficient calculations. This calculation method can help to avoid a major deficiency present at the limbs of the 1D stellar models.Comment: Accepted for publication in A&A. 4 pages, 2 figures, 2 tables. Full versions of tables 1 and 2 containing limb-darkening coefficients available at http://vega.lpl.arizona.edu/~sing

A small survey of the magnetic fields of planet-host stars

Using spectropolarimetry, we investigate the large-scale magnetic topologies of stars hosting close-in exoplanets. A small survey of ten stars has been done with the twin instruments TBL/NARVAL and CFHT/ESPaDOnS between 2006 and 2011. Each target consists of circular-polarization observations covering 7 to 22 days. For each of the 7 targets in which a magnetic field was detected, we reconstructed the magnetic field topology using Zeeman-Doppler imaging. Otherwise, a detection limit has been estimated. Three new epochs of observations of Tau Boo are presented, which confirm magnetic polarity reversal. We estimate that the cycle period is 2 years, but recall that a shorter period of 240 days can not still be ruled out. The result of our survey is compared to the global picture of stellar magnetic field properties in the mass-rotation diagram. The comparison shows that these giant planet-host stars tend to have similar magnetic field topologies to stars without detected hot-Jupiters. This needs to be confirmed with a larger sample of stars.Comment: Accepted for publication in Monthly Notices of The Royal Astronomical Societ