Results for "Raphaëlle Haywood"

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Determining the Mass of Kepler-78b With Nonparametric Gaussian Process EstimationJan 02 2015Jun 18 2015Kepler-78b is a transiting planet that is 1.2 times the radius of Earth and orbits a young, active K dwarf every 8 hours. The mass of Kepler-78b has been independently reported by two teams based on radial velocity measurements using the HIRES and HARPS-N ... More
A Kepler Study of Starspot Lifetimes with Respect to Light Curve Amplitude and Spectral TypeJul 26 2017Wide-field high precision photometric surveys such as Kepler have produced reams of data suitable for investigating stellar magnetic activity of cooler stars. Starspot activity produces quasi-sinusoidal light curves whose phase and amplitude vary as active ... More
Planet Size Distribution from the Kepler Mission and its Implications for Planet FormationJun 15 2018The size distribution of exoplanets is a bimodal division into two groups: Rocky planet (<2 Earth radii) and water-rich planet (>2 Earth radii) with or without gaseous envelope.
On the correlation between metallicity and the presence of giant planetsApr 28 2009The correlation between stellar metallicity and the presence of giant planets is well established. It has been tentatively explained by the possible increase of planet formation probability in stellar disks with enhanced amount of metals. However, there ... More
Revisiting two local constraints of the Galactic chemical evolutionSep 19 2006I review the uncertainties in two observational constraints of the Galactic disc chemical evolution: the metallicity distribution (MD) of long-lived dwarfs and the age-metallicity relation (AMR). It is shown first that the observed MD, designed with standard ... More
Galactic chemical evolution revisitedJan 08 2014Standard chemical evolution models based on long-term infall are affected by a number of problems, evidenced by the analysis of the most recent data. Among these: (1) models rely on the local metallicity distribution, assuming its shape is valid for the ... More
Radial mixing and the transition between the thick and thin Galactic discsMay 13 2008The analysis of the kinematics of solar neighbourhood stars shows that the low and high metallicity tails of the thin disc are populated by objects which orbital properties suggest an origin in the outer and inner galactic disc, respectively. Signatures ... More
A peculiarity of metal-poor stars with planets ?Apr 18 2008Stars with planets at intermediate metallicities ([-0.7,-0.2] dex) exhibit properties that differ from the general field stars. Thirteen stars with planets reported in this metallicity range belong to the thick disc, while only one planet have been detected ... More
On the metallicity of the Milky Way thin disc and photometric abundance scalesJun 28 2002The mean metallicity of the Milky Way thin disc in the solar neighbourhood is still a matter of debate, and has recently been subject to upward revision (Haywood, 2001). Our star sample was drawn from a set of solar neighbourhood dwarfs with photometric ... More
A revision of the solar neighbourhood metallicity distributionJul 04 2001We present a revised metallicity distribution of dwarfs in the solar neighbourhood. This distribution is centred on solar metallicity. We show that previous metallicity distributions, selected on the basis of spectral type, are biased against stars with ... More
A temperate rocky super-Earth transiting a nearby cool starApr 18 2017M dwarf stars, which have masses less than 60 per cent that of the Sun, make up 75 per cent of the population of the stars in the Galaxy [1]. The atmospheres of orbiting Earth-sized planets are observationally accessible via transmission spectroscopy ... More
A second terrestrial planet orbiting the nearby M dwarf LHS 1140Aug 01 2018Nov 22 2018LHS 1140 is a nearby mid-M dwarf known to host a temperate rocky super-Earth (LHS 1140 b) on a 24.737-day orbit. Based on photometric observations by MEarth and Spitzer as well as Doppler spectroscopy from HARPS, we report the discovery of an additional ... More
The Galactic structure and chemical evolution traced by the population of planetary nebulaeMar 03 2010We use an extended and homogeneous data set of Galactic planetary nebulae (PNe) to study the metallicity gradients and the Galactic structure and evolution. The most up-to-date abundances, distances (calibrated with Magellanic Cloud PNe) have been employed, ... More
Precise Masses in the WASP-47 SystemSep 29 2017We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ~19 hour orbit, and a Neptune in a ... More
On the distances of planetary nebulaeSep 11 2014Oct 14 2014We reconsider calibration of statistical distance scales for planetary nebulae, examining precision and systematic error for various distance methods used as well as the scales themselves. A different calibration strategy, one based on precise trigonometric ... More
Practical Reduction of Edge Flip Sequences in Two-Dimensional TriangulationsOct 09 2013The development of laser scanning techniques has popularized the representation of 3D shapes by triangular meshes with a large number of vertices. Compression techniques dedicated to such meshes have emerged, which exploit the idea that the connectivity ... More
A Control Forced Concurrent Precursor Method for LES InflowDec 11 2018With the increased application of large eddy simulation techniques, the generation of realistic turbulence at inflow boundaries is crucial for the accuracy of a simulation. The Control Forced Concurrent Precursor Method (CFCPM) proposed in this work combines ... More
Sparse Geometric Representation Through Local Shape ProbingDec 07 2016Shape analysis is very often performed by segmenting the shape into smooth surface parts that can be further classified using a set of predefined primitives such as planes, cylinders or spheres. Hence the shape is generally assumed to be manifold and ... More
Tree-based Reconstruction of Ecological Network from Abundance DataMay 07 2019The behavior of ecological systems mainly relies on the interactions between the species it involves. In many situations, these interactions are not observed and have to be inferred from species abundance data. To be relevant, any reconstruction network ... More
Sparse Geometric Representation Through Local Shape ProbingDec 07 2016Nov 02 2017We propose a new shape analysis approach based on the non-local analysis of local shape variations. Our method relies on a novel description of shape variations, called Local Probing Field (LPF), which describes how a local probing operator transforms ... More
Wakes in stratified atmospheric boundary layer flows: an LES investigationJan 18 2019Large eddy simulations and three-dimensional proper orthogonal decomposition were used to study the interaction between a large stationary and moving bluff body and a high Reynolds number stably-stratified turbulent boundary layer. An immersed boundary ... More
A 1.9 Earth radius rocky planet and the discovery of a non-transiting planet in the Kepler-20 systemAug 24 2016Kepler-20 is a solar-type star (V = 12.5) hosting a compact system of five transiting planets, all packed within the orbital distance of Mercury in our own Solar System. A transition from rocky to gaseous planets with a planetary transition radius of ... More
The Kepler-19 system: a thick-envelope super-Earth with two Neptune-mass companions characterized using Radial Velocities and Transit Timing VariationsMar 20 2017We report a detailed characterization of the Kepler-19 system. This star was previously known to host a transiting planet with a period of 9.29 days, a radius of 2.2 R$_\oplus$ and an upper limit on the mass of 20 M$_\oplus$. The presence of a second, ... More
The Milky Way stellar populations in CFHTLS fieldsNov 02 2011We investigate the characteristics of the thick disk in the Canada - France - Hawaii - Telescope Legacy Survey (CFHTLS) fields, complemented at bright magnitudes with Sloan Digital Sky Survey (SDSS) data. The ([Fe/H], Z) distributions are derived in the ... More
A Milky Way with a massive, centrally concentrated thick disc: new Galactic mass models for orbit computationsNov 23 2016In this work, two new axisymmetric models for the Galactic mass distribution are presented. Motivated by recent results, these two models include the contribution of a stellar thin disc and of a thick disc, as massive as the thin counterpart but with ... More
An ultra-short period rocky super-Earth with a secondary eclipse and a Neptune-like companion around K2-141Jan 10 2018Ultra-short period (USP) planets are a class of low mass planets with periods shorter than one day. Their origin is still unknown, with photo-evaporation of mini-Neptunes and in-situ formation being the most credited hypotheses. Formation scenarios differ ... More
Enhanced shot noise of multiple Andreev reflections in a carbon nanotube quantum dot in SU(2) and SU(4) Kondo regimesMay 21 2018The sensitivity of shot noise to the interplay between Kondo correlations and superconductivity is investigated in a carbon nanotube quantum dot connected to superconducting electrodes. Depending on the gate voltage, the SU(2) and SU(4) Kondo unitary ... More
Quantifying stellar radial migration in an N-body simulation: blurring, churning, and the outer regions of galaxy discsJan 04 2015May 06 2015Radial stellar migration in galactic discs has received much attention in studies of galactic dynamics and chemical evolution, but remains a dynamical phenomenon that needs to be fully quantified. In this work, using a Tree-SPH simulation of an Sb-type ... More
Mergers, tidal interactions, and mass exchange in a population of disc globular clustersSep 12 2018We present the results of a self-consistent $N$-body simulation following the evolution of a primordial population of thick disc globular clusters (GCs). We study how the internal properties of such clusters evolve under the action of mutual interactions, ... More
Reducing activity-induced variations in a radial-velocity time series of the Sun as a starApr 11 2019The radial velocity of the Sun as a star is affected by its surface convection and magnetic activity. The moments of the cross-correlation function between the solar spectrum and a binary line mask contain information about the stellar radial velocity ... More
Estimation of urinary stone composition by automated processing of CT imagesSep 12 2009The objective of this article was developing an automated tool for routine clinical practice to estimate urinary stone composition from CT images based on the density of all constituent voxels. A total of 118 stones for which the composition had been ... More
Clues to the formation of the Milky Way's thick diskApr 08 2015Apr 10 2015We analyse the chemical properties of a set of solar vicinity stars, and show that the small dispersion in abundances of \alpha-elements at all ages provides evidence that the SFH has been uniform throughout the thick disk. In the context of long time ... More
Clumpy streams in a smooth dark halo: the case of Palomar 5Sep 03 2012Sep 05 2012By means of direct N-body simulations and simplified numerical models, we study the formation and characteristics of the tidal tails around Palomar 5, along its orbit in the Milky Way potential. Unlike previous findings, we are able to reproduce the substructures ... More
On the origin of the clumpy streams of Palomar 5Feb 06 2013Apr 24 2013In this paper we report a study (see Mastrobuono-Battisti et al., 2012) about the formation and characteristics of the tidal tails around Palomar 5 along its orbit in the Milky Way potential, by means of direct N-body simulations and simplified numerical ... More
Mergers, tidal interactions, and mass exchange in a population of disc globular clusters: II. Long-term evolutionNov 19 2018Globular clusters (GCs), the oldest stellar systems observed in the Milky Way, have for long been considered single stellar populations. As such, they provided an ideal laboratory to understand stellar dynamics and primordial star formation processes. ... More
Hiding its age: the case for a younger bulgeJun 13 2016The determination of the age of the bulge has led to two contradictory results. On the one side, the color-magnitude diagrams in different bulge fields seem to indicate a uniformly old ($>$10 Gyr) population. On the other side, individual ages derived ... More
Stellar metallicity variations across spiral arms in disk galaxies with multiple populationsJan 26 2018This letter studies the formation of azimuthal metallicity variations in the disks of spiral galaxies in the absence of initial radial metallicity gradients. Using high-resolution $N$-body simulations, we model composite stellar discs, made of kinematically ... More
Radial mixing in the outer Milky Way disk caused by an orbiting satelliteMar 10 2009Apr 24 2009Using test particle simulations we examine the structure of the outer Galactic disk as it is perturbed by a satellite in a tight eccentric orbit about the Galaxy. A satellite of mass a few times 10^9 Msol can heat the outer Galactic disk, excite spiral ... More
Long-term radial-velocity variations of the Sun as a star: The HARPS viewJan 21 2016Jan 22 2016Stellar radial velocities play a fundamental role in the discovery of extrasolar planets and the measurement of their physical parameters as well as in the study of stellar physical properties. We investigate the impact of the solar activity on the radial ... More
Radial migration in a stellar galactic disc with thick componentsJan 08 2018Mar 07 2018We study how migration affects stars of a galaxy with a thin stellar disc and thicker stellar components. The simulated galaxy has a strong bar and lasting spiral arms. We find that the amplitude of the churning (change in angular momentum) is similar ... More
Universality of Non-equilibrium Fluctuations in Strongly Correlated Quantum LiquidsDec 02 2015Interacting quantum many-body systems constitute a fascinating playground for researchers since they form quantum liquids with correlated ground states and low-lying excitations, which exhibit universal behaviour. In fermionic systems, such quantum liquids ... More
Radial Velocity Prospects Current and Future: A White Paper Report prepared by the Study Analysis Group 8 for the Exoplanet Program Analysis Group (ExoPAG)Mar 05 2015Mar 09 2015[Abridged] The Study Analysis Group 8 of the NASA Exoplanet Analysis Group was convened to assess the current capabilities and the future potential of the precise radial velocity (PRV) method to advance the NASA goal to "search for planetary bodies and ... More
Quantum Fluctuations along Symmetry Crossover in Kondo-correlated Quantum DotApr 14 2017May 12 2017Universal properties of entangled many-body states are controlled by their symmetry and quantum fluctuations. By magnetic-field tuning of the spin-orbital degeneracy in a Kondo-correlated quantum dot, we have modified quantum fluctuations to directly ... More
Signatures of radial migration in barred galaxies: Azimuthal variations in the metallicity distribution of old starsJan 11 2013By means of N-body simulations, we show that radial migration in galaxy disks, induced by bar and spiral arms, leads to significant azimuthal variations in the metallicity distribution of old stars at a given distance from the galaxy center. Metals do ... More
The age structure of stellar populations in the solar vicinity. Clues of a two-phase formation history of the Milky Way diskMay 20 2013Oct 23 2013We analyze high quality abundances data of solar neighborhood stars and show that there are two distinct regimes of [alpha/Fe] versus age which we identify as the epochs of the thick and thin disk formation. A tight correlation between metallicity and ... More
Bar quenching in gas-rich galaxiesSep 11 2017Galaxy surveys have suggested that rapid and sustained decrease in the star-formation rate, "quenching", in massive disk galaxies is frequently related to the presence of a bar. Optical and near-IR observations reveal that nearly 60% of disk galaxies ... More
The disc origin of the Milky Way bulge: II. Dissecting the chemo-morphological relations using N-body simulations and APOGEEFeb 01 2018There is a long-standing debate on the origin of the metal-poor stellar populations of the Milky Way (MW) bulge, with the two leading scenarios being that these populations are either i) part of a classical metal-poor spheroid or ii) the same population ... More
When the Milky Way turned off the lights: APOGEE provides evidence of star formation quenching in our GalaxyJan 12 2016Jun 10 2016Quenching, the cessation of star formation, is one of the most significant events in the life cycle of galaxies. We show here the first evidence that the Milky Way experienced a generalised quenching of its star formation at the end of its thick disk ... More
Phylogeny of the Milky Way's inner disk and bulge populations: Implications for gas accretion, (the lack of) inside-out thick disk formation, and quenchingFeb 27 2018We show that the bulge and the disk of the Milky Way (MW) at R$\lesssim$7~kpc are well described by a unique chemical evolution and a two-phase star-formation history (SFH). We argue that the populations within this inner disk, not the entire disk, are ... More
In disguise or out of reach: first clues about in-situ and accreted stars in the stellar halo of the Milky Way from Gaia DR2May 07 2018Jul 06 2018We investigate the nature of the double color-magnitude sequence observed in the Gaia DR2 HR diagram of stars with high transverse velocities. The stars in the reddest-color sequence are likely dominated by the dynamically-hot tail of the thick disk population. ... More
Searching for a kinematic signature of the moderately metal-poor stars in the Milky Way bulge using N-body simulationsMar 26 2018Although there is consensus that metal-rich stars in the Milky Way bulge are formed via secular evolution of the thin disc, the origin of their metal-poor counterparts is still under debate. Two different origins have been invoked for metal-poor stars: ... More
Constraining Stellar Photospheres as an Essential Step for Transmission Spectroscopy of Small ExoplanetsMar 14 2019Transmission spectra probe the atmospheres of transiting exoplanets, but these observations are also subject to signals introduced by magnetic active regions on host stars. Here we outline scientific opportunities in the next decade for providing useful ... More
Bars & boxy/peanut bulges in thin & thick discs: I. Morphology and line-of-sight velocities of a fiducial modelApr 03 2017May 30 2017We explore trends in the morphology and line-of-sight (los) velocity of stellar populations in the inner regions of disc galaxies, using N-body simulations with both a thin (kinematically cold) and a thick (kinematically hot) disc which form a bar and ... More
Review of Conformally Flat Approximation for Binary Neutron Star Initial ConditionsJan 07 2016Mar 16 2016The spatially conformally flat approximation (CFA) is a viable method to deduce initial conditions for the subsequent evolution of binary neutron stars employing the full Einstein equations. Here we review the status of the original formulation of the ... More
Star formation history of the Galactic bulge from deep HST imaging of low reddening windowsJan 04 2018Apr 12 2018Despite the huge amount of photometric and spectroscopic efforts targetting the Galactic bulge over the past few years, its age distribution remains controversial owing to both the complexity of determining the age of individual stars and the difficult ... More
An Earth-sized planet with an Earth-like densityOct 30 2013Kepler-78 (KIC 8435766) was identified by Sanchis-Ojeda et al. (2013) as harbouring a transiting planet of 1.16 times the size of the Earth and an orbital period of only 8.5 hours. While the exquisite Kepler photometry was able to determine its radius ... More
On the kinematic detection of accreted streams in the Gaia era: a cautionary taleNov 22 2016The $\Lambda$CDM cosmological scenario predicts that our Galaxy should contain hundreds of stellar streams at the solar vicinity, fossil relics of the merging history of the Milky Way and more generally of the hierarchical growth of galaxies. Because ... More
Revisiting long-standing puzzles of the Milky Way: the Sun and its vicinity as typical outer disk chemical evolutionMar 07 2019We present a scenario of the chemical enrichment of the solar neighborhood that solves the G-dwarf problem by taking into account constraints on a larger scale. We argue that the Milky Way disk within 10 kpc has been enriched to solar metallicity by a ... More
The disc origin of the Milky Way bulge: On the necessity of the thick discJan 03 2019In the MW bulge, metal-rich stars form a strong bar and are more peanut-shaped than metal-poor stars. It has been recently claimed that this behavior is driven by the initial in-plane radial velocity dispersion of these populations, rather than by their ... More
The thick disc of the Galaxy: Sequel of a merging eventApr 26 1995Accurate characterization of thick disc properties from recent kinematic and photometric surveys provides converging evidences that this intermediate population is a sequel of the violent heating of early disc populations by a merging satellite galaxy. ... More
Revisiting long-standing puzzles of the Milky Way: the Sun and its vicinity as typical outer disk chemical evolutionMar 07 2019Mar 29 2019We present a scenario of the chemical enrichment of the solar neighborhood that solves the G-dwarf problem by taking into account constraints on a larger scale. We argue that the Milky Way disk within 10 kpc has been enriched to solar metallicity by a ... More
The Milky Way as a High Redshift Galaxy: The Importance of Thick Disk Formation in GalaxiesJun 11 2014We compare the star-formation history and dynamics of the Milky Way (MW) with the properties of distant disk galaxies. During the first ~4 Gyr of its evolution, the MW formed stars with a high star-formation intensity (SFI), Sigma_SFR~0.6 Msun/yr/kpc2 ... More
The Besancon Galaxy model renewed I. Constraints on the local star formation history from Tycho dataFeb 13 2014The understanding of Galaxy evolution can be facilitated by the use of population synthesis models, which allows us to test hypotheses on the star formation history, star evolution, and chemical and dynamical evolution of the Galaxy. The new version of ... More
Star formation history of the Galactic bulge from deep HST imaging of low reddening windowsJan 04 2018Despite the huge amount of photometric and spectroscopic efforts targetting the Galactic bulge over the past few years, its age distribution remains controversial owing to both the complexity of determining the age of individual stars and the difficult ... More
On the cosmic evolution of the specific star formation rateFeb 09 2015The apparent correlation between the specific star formation rate (sSFR) and total stellar mass (M_star) of galaxies is a fundamental relationship indicating how they formed their stellar populations. To attempt to understand this relation, we hypothesize ... More
A new look at the kinematics of the bulge from an N-body modelFeb 21 2016(Abridged) By using an N-body simulation of a bulge that was formed via a bar instability mechanism, we analyse the imprints of the initial (i.e. before bar formation) location of stars on the bulge kinematics, in particular on the heliocentric radial ... More
Reconstructing the star formation history of the Milky Way disc(s) from chemical abundancesOct 14 2014Nov 07 2014We develop a chemical evolution model in order to study the star formation history of the Milky Way. Our model assumes that the Milky Way is formed from a closed box-like system in the inner regions, while the outer parts of the disc experience some accretion. ... More
The disc origin of the Milky Way bulge: Dissecting the chemo-morphological relations using N-body simulations and APOGEEFeb 01 2018May 08 2018There is a long-standing debate on the origin of the metal-poor stellar populations of the Milky Way (MW) bulge, with the two leading scenarios being that these populations are either i) part of a classical metal-poor spheroid or ii) the same population ... More
Ballistic edge states in Bismuth nanowires revealed by SQUID interferometrySep 15 2016Spin-orbit interactions are known to have drastic effects on the band structure of heavy-element-based materials. Celebrated examples are the recently identified 3D and 2D topological insulators. In those systems transport takes place at surfaces or along ... More
Certified counting of roots of random univariate polynomialsDec 04 2014A challenging problem in computational mathematics is to compute roots of a high-degree univariate random polynomial. We combine an efficient multiprecision implementation for solving high-degree random polynomials with two certification methods, namely ... More
High-Energy Photon and Particle Effects onExoplanet Atmospheres and HabitabilityMar 29 2019It is now recognized that energetic stellar photon and particle radiation evaporates and erodes planetary atmospheres and controls upper atmospheric chemistry. Key exoplanet host stars will be too faint at X-ray wavelengths for accurate characterization ... More
The dominant epoch of star formation in the Milky Way formed the thick discJan 08 2014We report the first robust measurement of the Milky Way star formation history using the imprint left on chemical abundances of long-lived stars. The formation of the Galactic thick disc occurs during an intense star formation phase between 9.0 (z~1.5) ... More
Uncovering the planets and stellar activity of CoRoT-7 using only radial velocitiesJan 27 2016Feb 03 2016Stellar activity can induce signals in the radial velocities of stars, complicating the detection of orbiting low-mass planets. We present a method to determine the number of planetary signals present in radial-velocity datasets of active stars, using ... More
The echo of the bar buckling: phase-space spirals in Gaia DR2Nov 22 2018Jan 29 2019Using a single N-body simulation ($N=0.14\times 10^9$) we explore the formation, evolution and spatial variation of the phase-space spirals similar to those recently discovered by Antoja et al. in the Milky Way disk, with Gaia DR2. For the first time ... More
What the Milky Way bulge reveals about the initial metallicity gradients in the discOct 18 2017Oct 31 2017We examine the metallicity trends in the Milky Way (MW) bulge - using APOGEE DR13 data - and explore their origin by comparing two N-body models of isolated galaxies which develop a bar and a boxy/peanut (b/p) bulge. Both models have been proposed as ... More
The Milky Way has no in-situ halo but it has a thick disc. Composition of the stellar halo and age-dating the last significant merger with Gaia DR2 and APOGEEDec 19 2018Previous studies based on the analysis of Gaia DR2 data have revealed that accreted stars, possibly originating from a single progenitor satellite, are a significant component of the halo of our Galaxy, potentially constituting most of the halo stars ... More
Mapping a stellar disk into a boxy bulge: The outside-in part of the Milky Way bulge formationApr 01 2014Apr 16 2014By means of idealized, dissipationless N-body simulations which follow the formation and subsequent buckling of a stellar bar, we study the characteristics of boxy/peanut-shaped bulges and compare them with the properties of the stellar populations in ... More
Why the Milky Way's bulge is not only a bar formed from a cold thin diskNov 05 2014By analyzing a N-body simulation of a bulge formed simply via a bar instability mechanism operating on a kinematically cold stellar disk, and by comparing the results of this analysis with the structural and kinematic properties of the main stellar populations ... More
On the ridges, undulations & streams in Gaia DR2: Linking the topography of phase-space to the orbital structure at the OLR of an N-body barJan 22 2019We explore the origin of phase-space substructures in the disc of the Milky Way, such as the ridges in the $V_{\phi}$-$r$ plane, the undulations in the $V_{\phi}$-$r$-$V_r$ space and the streams in the $V_{\phi}$-$V_r$ plane, seen in the second Gaia data ... More
Non-Fickian Diffusion and the Accumulation of Methane Bubbles in Deep-Water SedimentsNov 29 2010Dec 25 2013In the absence of fractures, methane bubbles in deep-water sediments can be immovably trapped within a porous matrix by surface tension. The dominant mechanism of transfer of gas mass therefore becomes the diffusion of gas molecules through porewater. ... More
Stellar Surface Magneto-Convection as a Source of Astrophysical Noise II. Center-to-Limb Parameterisation of Absorption Line Profiles and Comparison to ObservationsJul 30 2018Sep 11 2018Manifestations of stellar activity (such as star-spots, plage/faculae, and convective flows) are well known to induce spectroscopic signals often referred to as astrophysical noise by exoplanet hunters. For example, setting an ultimate goal of detecting ... More
Metallicity and kinematics of the bar in-situJan 09 2014Constraints on the Galactic bulge/bar structure and formation history from stellar kinematics and metallicities mainly come from relatively high-latitude fields (|b|>4) where a complex mix of stellar population is seen. We aim here to constrain the formation ... More
Planets and Stellar Activity: Hide and Seek in the CoRoT-7 systemJul 03 2014Since the discovery of the transiting super-Earth CoRoT-7b, several investigations have yielded different results for the number and masses of planets present in the system, mainly owing to the star's high level of activity. We re-observed CoRoT-7 in ... More
Ubv CCD Standards Near 5C1 Radio Sources at Intermediate Galactic Latitude-IJul 25 1994We have been doing a photometric and astrometric sample survey programme on Schmidt plates in a few selected directions in the Galaxy with an aim to study galactic stellar populations. In order to calibrate Schmidt plates photometrically, it is necessary ... More
Understanding Stellar Contamination in Exoplanet Transmission Spectra as an Essential Step in Small Planet CharacterizationMar 23 2018Transmission spectroscopy during planetary transits is expected to be a major source of information on the atmospheres of small (approximately Earth-sized) exoplanets in the next two decades. This technique, however, is intrinsically affected by stellar ... More
Spectroscopic Survey of the Galaxy with Gaia II. The expected science yield from the Radial Velocity SpectrometerJun 03 2005The Gaia mission is designed as a Galaxy explorer, and will measure simultaneously, in a survey mode, the five or six phase space parameters of all stars brighter than 20th magnitude, as well as providing a description of their astrophysical characteristics. ... More
The hot Jupiter of the magnetically-active weak-line T Tauri star V830 TauNov 07 2016We report results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star V830 Tau and its recently-detected newborn close-in giant planet. Our observations, carried out within the MaTYSSE programme, were spread over ... More
Spectroscopic survey of the Galaxy with Gaia I. Design and performance of the Radial Velocity SpectrometerSep 29 2004The definition and optimisation studies for the Gaia satellite spectrograph, the Radial Velocity Spectrometer (RVS), converged in late 2002 with the adoption of the instrument baseline. This paper reviews the characteristics of the selected configuration ... More
Radial-Velocity Fitting Challenge. II. First results of the analysis of the data setSep 13 2016Radial-velocity (RV) signals induce RV variations an order of magnitude larger than the signal created by the orbit of Earth-twins, thus preventing their detection. The goal of this paper is to compare the efficiency of the different methods used to deal ... More
Three years of Sun-as-a-star radial-velocity observations on the approach to solar minimumApr 27 2019The time-variable velocity fields of solar-type stars limit the precision of radial-velocity determinations of their planets' masses, obstructing detection of Earth twins. Since 2015 July we have been monitoring disc-integrated sunlight in daytime using ... More
The Mass of Kepler-93b and The Composition of Terrestrial PlanetsDec 30 2014Kepler-93b is a 1.478 +/- 0.019 Earth radius planet with a 4.7 day period around a bright (V=10.2), astroseismically-characterized host star with a mass of 0.911+/-0.033 solar masses and a radius of 0.919+/-0.011 solar radii. Based on 86 radial velocity ... More
Revisiting the transits of CoRoT-7b at a lower activity levelJul 30 2014CoRoT-7b, the first super-Earth with measured radius discovered, has opened the new field of rocky exoplanets characterisation. To better understand this interesting system, new observations were taken with the CoRoT satellite. During this run 90 new ... More
Characterization of the Kepler-101 planetary system with HARPS-N. A hot super-Neptune with an Earth-sized low-mass companionSep 16 2014We report on the characterization of the Kepler-101 planetary system, thanks to a combined DE-MCMC analysis of Kepler data and forty radial velocities obtained with the HARPS-N spectrograph. This system was previously validated by Rowe et al. (2014) and ... More
The Kepler-10 planetary system revisited by HARPS-N: A hot rocky world and a solid Neptune-mass planetMay 30 2014Kepler-10b was the first rocky planet detected by the Kepler satellite and con- firmed with radial velocity follow-up observations from Keck-HIRES. The mass of the planet was measured with a precision of around 30%, which was insufficient to constrain ... More
K2-263b: A 50-day period sub-Neptune with a mass measurement using HARPS-NAug 24 2018Sep 26 2018This paper reports on the validation and mass measurement of K2-263b, a sub-Neptune orbiting a quiet G9V star. Using K2 data from campaigns C5 and C16, we find this planet to have a period of $50.818947\pm 0.000094$ days and a radius of $2.41\pm0.12$ ... More
An accurate mass determination for Kepler-1655b, a moderately-irradiated world with a significant volatile envelopeMar 23 2018We present the confirmation of a small, moderately-irradiated (F = 155 +/- 7 Fearth) Neptune with a substantial gas envelope in a P=11.8728787+/-0.0000085-day orbit about a quiet, Sun-like G0V star Kepler-1655. Based on our analysis of the Kepler light ... More
The Canada-France Imaging Survey: First results from the u-band componentAug 21 2017The Canada-France Imaging Survey (CFIS) will map the northern high Galactic latitude sky in the $u$-band ("CFIS-u", 10,000$\, {\rm deg^2}$) and in the $r$-band ("CFIS-r", 5,000$\, {\rm deg^2}$), enabling a host of stand-alone science investigations, and ... More
GYES, a multifibre spectrograph for the CFHTSep 19 2010We have chosen the name of GYES, one of the mythological giants with one hundred arms, offspring of Gaia and Uranus, for our instrument study of a multifibre spectrograph for the prime focus of the Canada-France-Hawaii Telescope. Such an instrument could ... More
Masses and radii for the three super-Earths orbiting GJ 9827, and implications for the composition of small exoplanetsDec 18 2018Jan 11 2019Super-Earths belong to a class of planet not found in the Solar System, but which appear common in the Galaxy. Given that some super-Earths are rocky, while others retain substantial atmospheres, their study can provide clues as to the formation of both ... More