Results for "B. Mosser"

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The CoRoT-GES Collaboration. Improving Red Giants spectroscopic surface gravity and abundances with asteroseismologySep 14 2016Nowadays large spectroscopic surveys, like the Gaia-ESO Survey (GES), provide unique stellar databases for better investigating the formation and evolution of our Galaxy. Great attention must be paid to the accuracy of the basic stellar properties derived: ... More
On detecting the large separation in the autocorrelation of stellar oscillation times seriesSep 04 2009Oct 28 2009The observations carried out by the space missions CoRoT and Kepler provide a large set of asteroseismic data. Their analysis requires an efficient procedure first to determine if the star is reliably showing solar-like oscillations, second to measure ... More
Period spacings in red giants II. Automated measurementFeb 16 2016The space missions CoRoT and Kepler have provided photometric data of unprecedented quality for asteroseismology. A very rich oscillation pattern has been discovered for red giants, including mixed modes that are used to decipher the red giants interiors. ... More
Red giants seismologyOct 17 2013The space-borne missions CoRoT and Kepler are indiscreet. With their asteroseismic programs, they tell us what is hidden deep inside the stars. Waves excited just below the stellar surface travel throughout the stellar interior and unveil many secrets: ... More
Evolution of the gravity offset of mixed modes in RGB starsMay 14 2019Observations of mixed modes in evolved low-mass stars enable us to probe the properties of not only the outer envelope of these stars, but also their deep layers. Among the seismic parameters associated with mixed modes, the gravity offset, denoted with ... More
Asteroseismology of Procyon with SOPHIEDec 09 2007This paper reports a 9-night asteroseismic observation program conducted in January 2007 with the new spectrometer Sophie at the OHP 193-cm telescope, on the F5 IV-V target Procyon A. This first asteroseismic program with Sophie was intended to test the ... More
Reconstruction of three-dimensional porous media using generative adversarial neural networksApr 11 2017To evaluate the variability of multi-phase flow properties of porous media at the pore scale, it is necessary to acquire a number of representative samples of the void-solid structure. While modern x-ray computer tomography has made it possible to extract ... More
DeepFlow: History Matching in the Space of Deep Generative ModelsMay 14 2019The calibration of a reservoir model with observed transient data of fluid pressures and rates is a key task in obtaining a predictive model of the flow and transport behaviour of the earth's subsurface. The model calibration task, commonly referred to ... More
An abundance study of the red giants in the seismology fields of the CoRoT satelliteOct 10 2012A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. The optical spectra obtained for 19 targets have been used to accurately estimate their fundamental ... More
Constraining stellar physics from red-giant stars in binaries - stellar rotation, mixing processes and stellar activityNov 04 2016The unparalleled photometric data obtained by NASA's Kepler Space Telescope has led to an improved understanding of stellar structure and evolution - in particular for solar-like oscillators in this context. Binary stars are fascinating objects. Because ... More
Period spacings in red giants; III. Coupling factors of mixed modesDec 26 2016The power of asteroseismology relies on the capability of global oscillations to infer the stellar structure. For evolved stars, we benefit from unique information directly carried out by mixed modes that probe their radiative cores. This third article ... More
Seismic probing of the first dredge-up event through the eccentric red-giant & red-giant spectroscopic binary KIC9163796Dec 14 2017Jan 13 2018Binaries in double-lined spectroscopic systems provide a homogeneous set of stars. Differences of parameters, such as age or initial conditions, which otherwise would have strong impact on the stellar evolution, can be neglected. The observed differences ... More
An alternative to mode fittingJun 29 2010The space mission CoRoT provides us with a large amount of high-duty cycle long-duration observations. Mode fitting has proven to be efficient for the complete and detailed analysis of the oscillation pattern, but remains time consuming. Furthermore, ... More
Red giant seismology: observationsOct 27 2012The CoRoT and Kepler missions provide us with thousands of red-giant light curves that allow a very precise asteroseismic study of these objects. Before CoRoT and Kepler, the red-giant oscillation patterns remained obscure. Now, these spectra are much ... More
Seismic indices -- a deep look inside evolved starsDec 27 2015Independent of stellar modelling, global seismic parameters of red giants provide unique information on the individual stellar properties as well as on stellar evolution. They allow us to measure key stellar parameters, such as the stellar mass and radius, ... More
Stellar oscillations - the adiabatic caseSep 27 2015This lecture on adiabatic oscillations is intended to present the basis of asteroseismology and to serve as an introduction for other lectures of the EES 2014. It also exposes the state-of-the-art of solar-like oscillation analysis, as revealed by the ... More
Surface-effect corrections for solar-like oscillations using 3D hydrodynamical simulationsOct 01 2015The space-borne missions have provided us with a wealth of high-quality observational data that allows for seismic inferences of stellar interiors. This requires the computation of precise and accurate theoretical frequencies, but imperfect modeling of ... More
Seismic performanceDec 31 2018Asteroseismology is a unique tool that can be used to study the interior of stars and hence deliver unique information for the studiy of stellar physics, stellar evolution, and Galactic archaeology. We aim to develop a simple model of the information ... More
Theoretical power spectra of mixed modes in low mass red giant starsSep 22 2014CoRoT and Kepler observations of red giant stars revealed very rich spectra of non-radial solar-like oscillations. Of particular interest was the detection of mixed modes that exhibit significant amplitude, both in the core and at the surface of the stars. ... More
The underlying physical meaning of the $ν_{\rm max}-ν_{\rm c}$ relationApr 04 2011Apr 05 2011Asteroseismology of stars that exhibit solar-like oscillations are enjoying a growing interest with the wealth of observational results obtained with the CoRoT and Kepler missions. In this framework, scaling laws between asteroseismic quantities and stellar ... More
Period spacings in red giants IV: Toward a complete description of the mixed-mode patternJul 22 2018Jul 28 2018Oscillation modes with a mixed character, as observed in evolved low-mass stars, are highly sensitive to the physical properties of the innermost regions. Measuring their properties is therefore extremely important to probe the core, but requires some ... More
Period spacings in red giants I. Disentangling rotation and revealing core structure discontinuitiesSep 21 2015Asteroseismology allows us to probe the physical conditions inside the core of red giant stars. This relies on the properties of the global oscillations with a mixed character that are highly sensitive to the physical properties of the core. However, ... More
On the seismic scaling relations $Δν- \barρ$ and $ν_{\rm max}-ν_{\rm c}$Jul 11 2013Scaling relations between asteroseismic quantities and stellar parameters are essential tools for studying stellar structure and evolution. We will address two of them, namely, the relation between the large frequency separation ($\Delta \nu$) and the ... More
Asteroseismic surface gravity for evolved starsMay 28 2013Context: Asteroseismic surface gravity values can be of importance in determining spectroscopic stellar parameters. The independent log(g) value from asteroseismology can be used as a fixed value in the spectroscopic analysis to reduce uncertainties due ... More
Short-lived spots in solar-like stars as observed by CoRoTAug 17 2009Sep 06 2009Context. CoRoT light curves have an unprecedented photometric quality, having simultaneously a high signal-to-noise ratio, a long time span and a nearly continuous duty-cycle. Aims. We analyse the light-curves of four bright targets observed in the seismology ... More
Report on the First Workshop On the Globalization of Modeling LanguagesAug 25 2014The first edition of GEMOC workshop was co-located with the MODELS 2013 conference in Miami, FL, USA. The workshop provided an open forum for sharing experiences, problems and solutions related to the challenges of using of multiple modeling languages ... More
The red giants in NGC 6633 as seen with CoRoT, HARPS and SOPHIESep 08 2014The open cluster NGC 6633 was observed with CoRoT in 2011 and simultaneous high-resolution spectroscopy was obtained with the SOPHIE and HARPS spectrographs. One of the four targets was not found to be a cluster member. For all stars we provide estimates ... More
Seismic diagnostics for transport of angular momentum in stars 2. Interpreting observed rotational splittings of slowly-rotating red giant starsNov 07 2012Asteroseismology with the space-borne missions CoRoT and Kepler provides a powerful mean of testing the modeling of transport processes in stars. Rotational splittings are currently measured for a large number of red giant stars and can provide stringent ... More
HD 203608, a quiet asteroseismic target in the old galactic diskApr 19 2008A short observing run with the spectrometer Harps at the ESO 3.6-m telescope was conducted in order to continue exploring the asteroseismic properties of F type stars. In fact, Doppler observations of F type on the main sequence are demanding and remain ... More
Dipole modes with depressed amplitudes in red giants are mixed modesOct 12 2016Seismic observations have shown that a number of evolved stars exhibit low-amplitude dipole modes, which are referred to as depressed modes. Recently, these low amplitudes have been attributed to the presence of a strong magnetic field in the stellar ... More
Seismic evidence for a weak radial differential rotation in intermediate-mass core helium burning starsJun 08 2015The detection of mixed modes that are split by rotation in Kepler red giants has made it possible to probe the internal rotation profiles of these stars, which brings new constraints on the transport of angular momentum in stars. Mosser et al. (2012) ... More
Study of KIC 8561221 observed by Kepler: an early red giant showing depressed dipolar modesNov 27 2013The continuous high-precision photometric observations provided by the CoRoT and Kepler space missions have allowed us to better understand the structure and dynamics of red giants using asteroseismic techniques. A small fraction of these stars shows ... More
The connection between stellar granulation and oscillation as seen by the Kepler missionAug 04 2014The long and almost continuous observations by Kepler show clear evidence of a granulation background signal in a large sample of stars, which is interpreted as the surface manifestation of convection. It has been shown that its characteristic timescale ... More
Constraining the core-rotation rate in red-giant stars from Kepler space photometryNov 01 2012Rotation plays a key role in stellar structure and its evolution. Through transport processes which induce rotational mixing of chemical species and the redistribution of angular momentum, internal stellar rotation influences the evolutionary tracks in ... More
Helium signature in red giant oscillation patterns observed by KeplerMay 27 2015The space-borne missions CoRoT and Kepler have provided a large amount of precise photometric data. Among the stars observed, red giants show a rich oscillation pattern that allows their precise characterization. Long-duration observations allow for investigating ... More
The Correlation Between Mixing Length and Metallicity on the Giant Branch: Implications for Ages in the Gaia EraApr 04 2017In the updated APOGEE-Kepler catalog, we have asteroseismic and spectroscopic data for over 3000 first ascent red giants. Given the size and accuracy of this sample, these data offer an unprecedented test of the accuracy of stellar models on the post-main-sequence. ... More
Solar-like pulsating stars as distance indicators: G-K giants in the CoRoT and Kepler fieldsNov 18 2011The detection of radial and non-radial solar-like oscillations in thousands of G-K giants with CoRoT and Kepler is paving the road for detailed studies of stellar populations in the Galaxy. The available average seismic constraints allow a precise and ... More
Duty cycle of Doppler ground-based asteroseismic observationsDec 18 2006We report the observations of the clear sky fraction at the Concordia station during winter 2006, and derive from it the duty cycle for astronomical observations. Performance in duty cycle and observation duration promotes Dome C for efficient asteroseismic ... More
An automated pipeline for asteroseismology based on the autocorrelation of stellar time seriesJun 25 2010The autocorrelation of an asteroseismic time series has been identified as a powerful tool capable of providing measurements of the large frequency separations. The performance of this method has been assessed and quantified by Mosser & Appourchaux (2009). ... More
Rapid seismic domain transfer: Seismic velocity inversion and modeling using deep generative neural networksMay 22 2018Traditional physics-based approaches to infer sub-surface properties such as full-waveform inversion or reflectivity inversion are time-consuming and computationally expensive. We present a deep-learning technique that eliminates the need for these computationally ... More
Survival of a convective core in low-mass solar-like pulsator HD 203608Feb 18 2010A 5-night asteroseismic observation of the F8V star HD 203608 was conducted in August 2006 with HARPS, followed by an analysis of the data, and a preliminary modeling of the star (Mosser et al. 2008). The stellar parameters were significantly constrained, ... More
Solar-like oscillations in red giants observed with \textit{Kepler}: influence of increased timespan on global oscillation parametersJul 03 2012The length of the asteroseismic timeseries obtained from the Kepler satellite analysed here span 19 months. Kepler provides the longest continuous timeseries currently available, which calls for a study of the influence of the increased timespan on the ... More
Asteroseismic classification of stellar populations among 13000 red giants observed by KeplerFeb 04 2013Of the more than 150000 targets followed by the Kepler Mission, about 10% were selected as red giants. Due to their high scientific value, in particular for Galaxy population studies and stellar structure and evolution, their Kepler light curves were ... More
Red-giant seismic properties analyzed with CoRoTApr 03 2010The CoRoT 5-month long observation runs give us the opportunity to analyze a large variety of red-giant stars and to derive fundamental stellar parameters from their asteroseismic properties. We perform an analysis of more than 4\,600 CoRoT light curves ... More
Galactic Archaeology with CoRoT and APOGEE: Creating mock observations from a chemodynamical modelApr 26 2016In a companion paper, we have presented the combined asteroseismic-spectroscopic dataset obtained from CoRoT lightcurves and APOGEE infra-red spectra for 678 solar-like oscillating red giants in two fields of the Galactic disc (CoRoGEE). We have measured ... More
Angular momentum redistribution by mixed modes in evolved low-mass stars. I. Theoretical formalismMay 20 2015Seismic observations by the space-borne mission \emph{Kepler} have shown that the core of red giant stars slows down while evolving, requiring an efficient physical mechanism to extract angular momentum from the inner layers. Current stellar evolution ... More
Inpainting: A powerful interpolation technique for helio- and asteroseismic dataMar 26 2010Apr 30 2010In Helio- and asteroseismology, it is important to have continuous, uninterrupted, data sets. However, seismic observations usually contain gaps and we need to take them into account. In particular, if the gaps are not randomly distributed, they will ... More
Evidence for a sharp structure variation inside a red-giant starSep 06 2010The availability of precisely determined frequencies of radial and non-radial oscillation modes in red giants is finally paving the way for detailed studies of the internal structure of these stars. We look for the seismic signature of regions of sharp ... More
Asymptotic and measured large frequency separationsDec 07 2012Jan 02 2013With the space-borne missions CoRoT and Kepler, a large amount of asteroseismic data is now available. So-called global oscillation parameters are inferred to characterize the large sets of stars, to perform ensemble asteroseismology, and to derive scaling ... More
The CoRoT target HD 49933: 2- Comparison of theoretical mode amplitudes with observationsOct 21 2009Nov 18 2009From the seismic data obtained by CoRoT for the star HD 49933 it is possible, as for the Sun, to constrain models of the excitation of acoustic modes by turbulent convection. We compare a stochastic excitation model described in Paper I (arXiv:0910.4027) ... More
Stellar granulation as seen in disk-integrated intensity. II. Theoretical scaling relations compared with observationsSep 05 2013A large set of stars observed by CoRoT and Kepler shows clear evidence for the presence of a stellar background, which is interpreted to arise from surface convection, i.e., granulation. These observations show that the characteristic time-scale (tau_eff) ... More
Angular momentum redistribution by mixed modes in evolved low-mass stars. II. Spin-down of the core of red giants induced by mixed modesMay 20 2015The detection of mixed modes in subgiants and red giants by the CoRoT and \emph{Kepler} space-borne missions allows us to investigate the internal structure of evolved low-mass stars. In particular, the measurement of the mean core rotation rate as a ... More
Period-luminosity relations in evolved red giants explained by solar-like oscillationsOct 02 2013Oct 07 2013Solar-like oscillations in red giants have been investigated with CoRoT and Kepler, while pulsations in more evolved M giants have been studied with ground-based microlensing surveys. After 3.1 years of observation with Kepler, it is now possible to make ... More
Properties of oscillation modes in subgiant stars observed by KeplerFeb 18 2013Feb 26 2013Mixed modes seen in evolved stars carry information on their deeper layers that can place stringent constraints on their physics and on their global properties (mass, age, etc...). In this study, we present a method to identify and measure all oscillatory ... More
Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fieldsMar 18 2014A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. High-resolution FEROS and HARPS spectra were obtained as part of the ground-based follow-up campaigns ... More
Inferring mode inertias in evolved solar-like starsJan 21 2014Asteroseismology of evolved solar-like stars is experiencing a growing interest due to the wealth of observational data from space-borne instruments such as the \emph{CoRoT} and \emph{Kepler} spacecraft. In particular, the recent detection of mixed modes, ... More
Differential asteroseismic study of seismic twins observed by CoRoT; Comparison of HD 175272 with HD 181420Sep 08 2013The CoRoT short asteroseismic runs give us the opportunity to observe a large variety of late-type stars through their solar-like oscillations. We report the observation and modeling of the F5V star HD 175272. Our aim is to define a method for extracting ... More
Seismic diagnostics for transport of angular momentum in stars 1. Rotational splittings from the PMS to the RGBNov 06 2012Rotational splittings are currently measured for several main sequence stars and a large number of red giants with the space mission Kepler. This will provide stringent constraints on rotation profiles. Our aim is to obtain seismic constraints on the ... More
Evolutionary influences on the structure of red-giant acoustic oscillation spectra from 600d of Kepler observationsMar 14 2012Context: The Kepler space mission is reaching continuous observing times long enough to start studying the fine structure of the observed p-mode spectra. Aims: In this paper, we aim to study the signature of stellar evolution on the radial and p-dominated ... More
Conditioning of three-dimensional generative adversarial networks for pore and reservoir-scale modelsFeb 15 2018Geostatistical modeling of petrophysical properties is a key step in modern integrated oil and gas reservoir studies. Recently, generative adversarial networks (GAN) have been shown to be a successful method for generating unconditional simulations of ... More
Sounding stellar cores with mixed modesOct 17 2013The space-borne missions CoRoT and Kepler have opened a new era in stellar physics, especially for evolved stars, with precise asteroseismic measurements that help determine precise stellar parameters and perform ensemble astero seismology. This paper ... More
Stochastic reconstruction of an oolitic limestone by generative adversarial networksDec 07 2017Stochastic image reconstruction is a key part of modern digital rock physics and materials analysis that aims to create numerous representative samples of material micro-structures for upscaling, numerical computation of effective properties and uncertainty ... More
Stochastic seismic waveform inversion using generative adversarial networks as a geological priorJun 10 2018We present an application of deep generative models in the context of partial-differential equation (PDE) constrained inverse problems. We combine a generative adversarial network (GAN) representing an a priori model that creates subsurface geological ... More
Large-scale measurements of the red giant core rotation through asteroseismologyOct 16 2017Red giant stars are solar-like pulsators presenting mixed-modes. Such modes consist in a coupling between pressure waves propagating in the external convective envelope and gravity waves propagating in the radiative interior. Therefore, the red giant ... More
Measuring the core rotation of red giant starsDec 16 2016Red giant stars present mixed modes, which behave as pressure modes in the convective envelope and as gravity modes in the radiative interior. This mixed character allows to probe the physical conditions in their core. With the advent of long-duration ... More
Rapidly rotating red giantsNov 02 2016Stellar oscillations give seismic information on the internal properties of stars. Red giants are targets of interest since they present mixed modes, which behave as pressure modes in the convective envelope and as gravity modes in the radiative core. ... More
The universal red-giant oscillation pattern; an automated determination with CoRoT dataNov 08 2010The CoRoT and Kepler satellites have provided thousands of red-giant oscillation spectra. The analysis of these spectra requires efficient methods for identifying all eigenmode parameters. The assumption of new scaling laws allows us to construct a theoretical ... More
Weak Antilocalization and Spin Precession in Quantum WellsFeb 12 1996The results of magnetoconductivity measurements in GaInAs quantum wells are presented. The observed magnetoconductivity appears due to the quantum interference, which lead to the weak localization effect. It is established that the details of the weak ... More
HD 46375: seismic and spectropolarimetric analysis of a young Sun hosting a Saturn-like planetNov 11 2010HD 46375 is known to host a Saturn-like exoplanet orbiting at 0.04 AU from its host star. Stellar light reflected by the planet was tentatively identified in the 34-day CoRoT run acquired in October-November 2008. We constrain the properties of the magnetic ... More
The PLATO Solar-like Light-curve Simulator: A tool to generate realistic stellar light-curves with instrumental effects representative of the PLATO missionMar 07 2019Mar 23 2019The preparation of science objectives of the ESA's PLATO space mission will require the implementation of hare-and-hound exercises relying on the massive generation of representative simulated light-curves. We developed a light-curve simulator named the ... More
The Radial Velocity Experiment (RAVE): Fifth Data ReleaseSep 11 2016Nov 16 2016Data Release 5 (DR5) of the Radial Velocity Experiment (RAVE) is the fifth data release from a magnitude-limited (9< I < 12) survey of stars randomly selected in the southern hemisphere. The RAVE medium-resolution spectra ($R\sim7500$) covering the Ca-triplet ... More
Masses and ages for metal-poor stars: a pilot program combining asteroseismology and high-resolution spectroscopic follow-up of RAVE halo starsAug 26 2018Very metal-poor halo stars are the best candidates for being among the oldest objects in our Galaxy. Samples of halo stars with age determination and detailed chemical composition measurements provide key information for constraining the nature of the ... More
Internal rotation of the red-giant star KIC 4448777 by means of asteroseismic inversionNov 19 2015In this paper we study the dynamics of the stellar interior of the early red-giant star KIC 4448777 by asteroseismic inversion of 14 splittings of the dipole mixed modes obtained from {\it Kepler} observations. In order to overcome the complexity of the ... More
Solar-like oscillations in low-luminosity red giants: first results from KeplerJan 01 2010Jan 22 2010We have measured solar-like oscillations in red giants using time-series photometry from the first 34 days of science operations of the Kepler Mission. The light curves, obtained with 30-minute sampling, reveal clear oscillations in a large sample of ... More
Old puzzle, new insights: a lithium rich giant quietly burning helium in its coreFeb 25 2014About 1% of giant stars have been shown to have large surface Li abundances, which is unexpected according to standard stellar evolution models. Several scenarios for lithium production have been proposed, but it is still unclear why these Li-rich giants ... More
Internal rotation of red giants by asteroseismologyDec 19 2012We present an asteroseismic approach to study the dynamics of the stellar interior in red-giant stars by asteroseismic inversion of the splittings induced by the stellar rotation on the oscillation frequencies. We show preliminary results obtained for ... More
Galactic archaeology: mapping and dating stellar populations with asteroseismology of red-giant starsNov 01 2012Our understanding of how the Galaxy was formed and evolves is severely hampered by the lack of precise constraints on basic stellar properties such as distances, masses, and ages. Here, we show that solar-like pulsating red giants represent a well-populated ... More
Differential population studies using asteroseismology: solar-like oscillating giants in CoRoT fields LRc01 and LRa01Jan 08 2013Solar-like oscillating giants observed by the space-borne satellites CoRoT and Kepler can be used as key tracers of stellar populations in the Milky Way. When combined with additional photometric/spectroscopic constraints, the pulsation spectra of solar-like ... More
The PLATO Solar-like Light-curve Simulator: A tool to generate realistic stellar light-curves with instrumental effects representative of the PLATO missionMar 07 2019The preparation of science objectives of the ESA's PLATO space mission will require the implementation of hare-and-hound exercises relying on the massive generation of representative simulated light-curves. We developed a light-curve simulator named the ... More
Modelling a high-mass red giant observed by CoRoTNov 28 2011The G6 giant HR\,2582 (HD\,50890) was observed by CoRoT for approximately 55 days. Mode frequencies are extracted from the observed Fourier spectrum of the light curve. Numerical stellar models are then computed to determine the characteristics of the ... More
Mixed modes in red-giant stars observed with CoRoTMay 30 2011Jun 01 2011The CoRoT mission has provided thousands of red-giant light curves. The analysis of their solar-like oscillations allows us to characterize their stellar properties. Up to now, the global seismic parameters of the pressure modes remain unable to distinguish ... More
The K2 Galactic Archaeology Program Data Release 1: Asteroseismic results from Campaign 1Nov 29 2016NASA's K2 mission is observing tens of thousands of stars along the ecliptic, providing data suitable for large scale asteroseismic analyses to inform galactic archaeology studies. Its first campaign covered a field near the north galactic cap, a region ... More
Nanorods of Well-Defined Length and Monodisperse Cross-Section Obtained from Electrostatic Complexation of Nanoparticles with a Semiflexible BiopolymerOct 21 2012We show by combining small-angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (cryo-TEM) that anionic silica nanoparticles (SiNPs) assemble into well-defined 1D cluster when mixed with a dilute solution of semiflexible chitosan polycation. ... More
Testing the cores of first ascent red-giant stars using the period spacing of g modesDec 11 2015In the context of the determination of stellar properties using asteroseismology, we study the influence of rotation and convective-core overshooting on the properties of red-giant stars. We used models in order to investigate the effects of these mechanisms ... More
Pump-Probe Experiments on the Single-Molecule Magnet Fe8 : Measurement of Excited Level LifetimesAug 22 2007We present magnetization measurements on the single molecule magnet Fe8 in the presence of pulsed microwave radiation. A pump-probe technique is used with two microwave pulses with frequencies of 107 GHz and 118 GHz and pulse lengths of several nanoseconds ... More
Modeling Kepler Observations of Solar-like Oscillations in the Red-giant Star HD 186355Sep 05 2011Nov 28 2011We have analysed oscillations of the red giant star HD 186355 observed by the NASA Kepler satellite. The data consist of the first five quarters of science operations of Kepler, which cover about 13 months. The high-precision time-series data allow us ... More
Surface Activity and Oscillation Amplitudes of Red Giants in Eclipsing BinariesFeb 13 2014Among 19 red-giant stars belonging to eclipsing binary systems that have been identified in Kepler data, 15 display solar-like oscillations. We study whether the absence of mode detection in the remaining 4 is an observational bias or possibly evidence ... More
Energy Level Lifetimes in the Single-Molecule Magnet Fe_8 : Experiments and SimulationsDec 06 2007We present pump-probe measurements on the single-molecule magnet Fe_8 with microwave pulses having a length of several nanoseconds. The microwave radiation in the experiments is located in the frequency range between 104 GHz and 118 GHz. The dynamics ... More
Red giants observed by CoRoT and APOGEE: The evolution of the Milky Way's radial metallicity gradientAug 17 2016Nov 16 2016Using combined asteroseismic and spectroscopic observations of 418 red-giant stars close to the Galactic disc plane (6 kpc $<R_{\rm Gal}\lesssim13$ kpc, $|Z_{\rm Gal}|<0.3$ kpc), we measure the age dependence of the radial metallicity distribution in ... More
Red giants observed by CoRoT and APOGEE: The evolution of the Milky Way's radial metallicity gradientAug 17 2016Dec 20 2016Using combined asteroseismic and spectroscopic observations of 418 red-giant stars close to the Galactic disc plane (6 kpc $<R_{\rm Gal}\lesssim13$ kpc, $|Z_{\rm Gal}|<0.3$ kpc), we measure the age dependence of the radial metallicity distribution in ... More
Asteroseismology of red giants from the first four months of Kepler data: Global oscillation parameters for 800 starsOct 21 2010We have studied solar-like oscillations in ~800 red-giant stars using Kepler long-cadence photometry. The sample includes stars ranging in evolution from the lower part of the red-giant branch to the Helium main sequence. We investigate the relation between ... More
Red giants observed by CoRoT and APOGEE: The evolution of the Milky Way's radial metallicity gradientAug 17 2016Using combined asteroseismic and spectroscopic observations of 418 red-giant stars close to the Galactic disc plane (6 kpc $<R_{\rm Gal}\lesssim13$ kpc, $|Z_{\rm Gal}|<0.3$ kpc), we measure the age dependence of the radial metallicity distribution in ... More
An asteroseismic membership study of the red giants in three open clusters observed by Kepler: NGC6791, NGC6819, and NGC6811Jul 06 2011Studying star clusters offers significant advances in stellar astrophysics due to the combined power of having many stars with essentially the same distance, age, and initial composition. This makes clusters excellent test benches for verification of ... More
Solar-like oscillations in red giants observed with Kepler: comparison of global oscillation parameters from different methodsAug 17 2010The large number of stars for which uninterrupted high-precision photometric timeseries data are being collected with \textit{Kepler} and CoRoT initiated the development of automated methods to analyse the stochastically excited oscillations in main-sequence, ... More
Time-Series Analysis of Broadband Photometry of Neptune from K2Feb 09 2017We report here on our search for excess power in photometry of Neptune collected by the K2 mission that may be due to intrinsic global oscillations of the planet Neptune. To conduct this search, we developed new methods to correct for instrumental effects ... More
Amplitudes of solar-like oscillations: constraints from red giants in open clusters observed by KeplerJul 03 2011Scaling relations that link asteroseismic quantities to global stellar properties are important for gaining understanding of the intricate physics that underpins stellar pulsation. The common notion that all stars in an open cluster have essentially the ... More
Seismic and spectroscopic characterization of the solar-like pulsating CoRoT target HD 49385Mar 23 2010The star HD 49385 is the first G-type solar-like pulsator observed in the seismology field of the space telescope CoRoT. The satellite collected 137 days of high-precision photometric data on this star, confirming that it presents solar-like oscillations. ... More
Probing the core structure and evolution of red giants using gravity-dominated mixed modes observed with KeplerMar 03 2012We report for the first time a parametric fit to the pattern of the \ell = 1 mixed modes in red giants, which is a powerful tool to identify gravity-dominated mixed modes. With these modes, which share the characteristics of pressure and gravity modes, ... More
Investigating the properties of granulation in the red giants observed by KeplerOct 01 2011More than 1000 red giants have been observed by NASA/Kepler mission during a nearly continuous period of ~ 13 months. The resulting high-frequency resolution (< 0.03 muHz) allows us to study the granulation parameters of these stars. The granulation pattern ... More
Characterization of the power excess of solar-like oscillations in red giants with KeplerOct 05 2011We aim to describe the oscillation power excess observed in Kepler red giants, and to investigate empirical scaling relations governing these parameters. From these scalings relations, we derive new physical properties of red giant oscillations. Various ... More