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1. PLATO as it is: A legacy mission for Galactic archaeology

Author: A. Miglio, C. Chiappini, B. Mosser, G. R. Davies, K. Freeman, L. Girardi, P. Jofré, D. Kawata, B. M. Rendle, M. Valentini, L. Casagrande, W. J. Chaplin, G. Gilmore, K. Hawkins, B. Holl, T. Appourchaux, K. Belkacem, D. Bossini, K. Brogaard, M.‐J. Goupil, J. Montalbán, A. Noels, F. Anders, T. Rodrigues, G. Piotto, D. Pollacco, H. Rauer, C. Allende Prieto, P. P. Avelino, C. Babusiaux, C. Barban, B. Barbuy, S. Basu, F. Baudin, O. Benomar, O. Bienaymé, J. Binney, J. Bland‐Hawthorn, A. Bressan, C. Cacciari, T. L. Campante, S. Cassisi, J. Christensen‐Dalsgaard, F. Combes, O. Creevey, M. S. Cunha, R. S. Jong, P. Laverny, S. Degl'Innocenti, S. Deheuvels, É. Depagne, J. Ridder, P. Di Matteo, M. P. Di Mauro, M.‐A. Dupret, P. Eggenberger, Y. Elsworth, B. Famaey, S. Feltzing, R. A. García, O. Gerhard, B. K. Gibson, L. Gizon, M. Haywood, R. Handberg, U. Heiter, S. Hekker, D. Huber, R. Ibata, D. Katz, S. D. Kawaler, H. Kjeldsen, D. W. Kurtz, N. Lagarde, Y. Lebreton, M. N. Lund, S. R. Majewski, P. Marigo, M. Martig, S. Mathur, I. Minchev, T. Morel, S. Ortolani, M. H. Pinsonneault, B. Plez, P. G. Prada Moroni, D. Pricopi, A. Recio‐Blanco, C. Reylé, A. Robin, I. W. Roxburgh, M. Salaris, B. X. Santiago, R. Schiavon, A. Serenelli, S. Sharma, V. Silva Aguirre, C. Soubiran, M. Steinmetz, D. Stello, K. G. Strassmeier, P. Ventura, R. Ventura, N. A. Walton, and C. C. Worley
Published: 2017
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2. Amplitudes of Solar Gravity Modes: A Review

Author: K. Belkacem, C. Pinçon, and G. Buldgen
Subjects: Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: Solar gravity modes are considered as the {\it Rosetta Stone} for probing and subsequently deciphering the physical properties of the solar inner-most layers. Recent claims of positive detection therefore shed some new light on the long-standing issue of estimating solar gravity mode amplitudes. In this article, our objective is to review the theoretical efforts intended to predict solar gravity mode amplitudes. Because most of these studies assumed analogous driving and damping properties to those for the observed acoustic modes, we also provide a short overview of our current knowledge for these modes in the Sun and solar-type stars (which show solar-like oscillations) before diving into the specific problem of solar gravity modes. Finally, taking recent estimates into account, we conclude and confirm that the low-frequency domain (typically between $10\,\mu$Hz and $100\,\mu$Hz) is certainly more suited to focus on for detecting solar gravity modes. More precisely, around $60\,\mu$Hz, the theoretical estimates are slightly lower than the observational detection threshold as provided by the GOLF (Global Oscillations at Low Frequencies) instrument by about a factor of two only. This is typically within the current uncertainties associated with theoretical estimates and should motivate us for improving our knowledge on turbulence in the whole solar convective region, which is key for improving the accuracy of $g$-mode amplitude estimates. The recent detection of solar inertial modes (Gizon et al. 2021) combined with the continuous development of numerical simulations provide interesting prospects for future studies., Comment: Accepted for publication in Solar Physics
Published: 2022
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3. PLATO Hare-and-Hounds exercise: Asteroseismic model fitting of main-sequence solar-like pulsators

Author: Tiago L. Campante, M. L. Winther, M. T. Clara, Mário J. P. F. G. Monteiro, K. Belkacem, Kuldeep Verma, M. S. Cunha, Anthony Noll, V. Aguirre Børsen-Koch, Sarbani Basu, William J. Chaplin, Warrick H. Ball, Amalie Stokholm, Daniel R. Reese, J. L. Rørsted, Ian W. Roxburgh, Marie-Jo Goupil, Benard Nsamba, R. M. Ouazzani, S. Deheuvels, Joel J. M. Ong, Joergen Christensen-Dalsgaard, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Physics, Accuracy and precision, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Mode (statistics), FOS: Physical sciences, Astronomy and Astrophysics, Absolute value, Radius, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asteroseismology, Gravitation, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Range (statistics), Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract: Asteroseismology is a powerful tool to infer fundamental stellar properties. The use of these asteroseismic-inferred properties in a growing number of astrophysical contexts makes it vital to understand their accuracy. Consequently, we performed a hare-and-hounds exercise where the hares simulated data for 6 artificial main-sequence stars and the hounds inferred their properties based on different inference procedures. To mimic a pipeline such as that planned for the PLATO mission, all hounds used the same model grid. Some stars were simulated using the physics adopted in the grid, others a different one. The maximum relative differences found (in absolute value) between the inferred and true values of the mass, radius, and age were 4.32 per cent, 1.33 per cent, and 11.25 per cent, respectively. The largest systematic differences in radius and age were found for a star simulated assuming gravitational settling, not accounted for in the model grid, with biases of -0.88 per cent (radius) and 8.66 per cent (age). For the mass, the most significant bias (-3.16 per cent) was found for a star with a helium enrichment ratio outside the grid range. Moreover, a ~7 per cent dispersion in age was found when adopting different prescriptions for the surface corrections or shifting the classical observations by $\pm 1\sigma$. The choice of the relative weight given to the classical and seismic constraints also impacted significantly the accuracy and precision of the results. Interestingly, only a few frequencies were required to achieve accurate results on the mass and radius. For the age the same was true when at least one $l=2$ mode was considered., Comment: Accepted for publication in the Monthly Notices of the Royal Astronomical Society
Published: 2021

4. Coupling between turbulence and solar-like oscillations: A combined Lagrangian PDF/SPH approach

Author: J. Philidet, K. Belkacem, and M.-J. Goupil
Subjects: Plasma Physics (physics.plasm-ph), Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Fluid Dynamics (physics.flu-dyn), FOS: Physical sciences, Astronomy and Astrophysics, Physics - Fluid Dynamics, Solar and Stellar Astrophysics (astro-ph.SR), Physics - Plasma Physics
Abstract: The first paper of this series established a linear stochastic wave equation for solar-like p-modes, correctly taking the effect of turbulence thereon into account. In this second paper, we aim at deriving simultaneous expressions for the excitation rate, damping rate, and modal surface effect associated with any given p-mode, as an explicit function of the statistical properties of the turbulent velocity field. We reduce the stochastic wave equation to complex amplitude equations for the normal oscillating modes of the system. We then derive the equivalent Fokker-Planck equation for the real amplitudes and phases of all the oscillating modes of the system simultaneously. The effect of the finite-memory time of the turbulent fluctuations (comparable to the period of the modes) on the modes themselves is consistently and rigorously accounted for, by means of the simplified amplitude equation formalism. This formalism accounts for mutual linear mode coupling in full, and we then turn to the special single-mode case. This allows us to derive evolution equations for the mean energy and mean phase of each mode, from which the excitation rate, the damping rate, and the modal surface effect naturally arise. We show that the expression for the excitation rate of the modes is identical to previous results obtained through a different modelling approach, thus supporting the validity of the formalism presented here. We also recover the fact that the damping rate and modal surface effect correspond to the real and imaginary part of the same single complex quantity. We explicitly separate the different physical contributions to these observables, in particular the turbulent pressure contribution and the joint effect of the pressure-rate-of-strain correlation and the turbulent dissipation. We show that the former dominates for high-frequency modes and the latter for low-frequency modes., Accepted for publication in A&A. 23 pages, 2 figures
Published: 2022

5. Surface effects and turbulent pressure

Author: Friedrich Kupka, R. Samadi, J. Philidet, K. Belkacem, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Faculty of Mathematics [Vienna], University of Vienna [Vienna], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Convection, Work (thermodynamics), Buoyancy, Perturbation (astronomy), Flux, Astrophysics, engineering.material, 01 natural sciences, 0103 physical sciences, waves, Sun: oscillations, 010303 astronomy & astrophysics, convection, Physics, 010308 nuclear & particles physics, Empirical modelling, Astronomy and Astrophysics, Mechanics, Physics - Fluid Dynamics, Dissipation, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Turbulence kinetic energy, engineering, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The use of the full potential of stellar seismology is made difficult by the improper modeling of the upper-most layers of solar-like stars and their influence on the modeled frequencies. Our knowledge on these \emph{surface effects} has improved thanks to the use of 3D hydrodynamical simulations but the calculation of eigenfrequencies relies on empirical models for the description of the Lagrangian perturbation of turbulent pressure: the reduced-$\Gamma_1$ model (RGM) and the gas-$\Gamma_1$ model (GGM). Starting from the fully compressible turbulence equations, we derive both the GGM and RGM models using a closure to model the flux of turbulent kinetic energy. It is found that both models originate from two terms: the source of turbulent pressure due to compression produced by the oscillations and the divergence of the flux of turbulent pressure. It is also demonstrated that they are both compatible with the adiabatic approximation but also imply a number of questionable assumptions mainly regarding mode physics. Among others hypothesis, one has to neglect the Lagrangian perturbation of the dissipation of turbulent kinetic energy into heat and the Lagrangian perturbation of buoyancy work., Comment: 7 pages, 1 figure. Accepted as a Letter in Astronomy and Astrophysic
Published: 2021

6. Introduction

Author: K. Belkacem
Published: 2020

7. First-Principles Study of the New Half-Metallic Ferromagnetic Quaternary-Heusler Alloys NaXNO (X=Ca, Sr, Ba)

Author: L. Beldi, K. Belkacem, S. Amari, B. Bouhafs, and Y. Zaoui
Subjects: 010302 applied physics, Materials science, Condensed matter physics, Magnetism, Astrophysics::Instrumentation and Methods for Astrophysics, Computer Science::Computation and Language (Computational Linguistics and Natural Language and Speech Processing), 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Metal, Condensed Matter::Materials Science, Ferromagnetism, visual_art, 0103 physical sciences, visual_art.visual_art_medium, Computer Science::General Literature, Density functional theory, Electrical and Electronic Engineering, 0210 nano-technology, Quaternary
Abstract: The first-principles approach based on density functional theory (DFT) and the full-potential linearized augmented plane-wave method were employed to investigate the structural, elastic, electronic and magnetic properties of Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys. The generalized gradient approximation (GGA) as parameterized by Perdew, Burke and Ernzerhof (PBE) and the modified Becke–Johnson exchange potential were used. As far as we know, we present our results which for the first time quantitatively account for the electronic structures and magnetic properties of Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys. From the total energy calculation using three possible atomic configurations ([Formula: see text], [Formula: see text] and [Formula: see text]), it is found that the Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys are more stable in the ferromagnetic [Formula: see text]-phase. From our estimated elastic constants [Formula: see text], it is found that all the considered Heusler alloys are mechanically stable in the [Formula: see text]-phase. We have also investigated the robustness of the half-metallicity with respect to the variation of lattice constants in these alloys. We have found that these alloys are half-metallic ferromagnets (HMFs) with a magnetic moment of 2[Formula: see text][Formula: see text] per formula unit at their equilibrium volumes. The spin-polarized electronic band structure and density of states of these quaternary half-Heusler alloys calculated by GGA (mBJ-GGA) show that the minority spin channels have metallic nature and the majority spin channels have a semiconductor character with half-metallic gaps of 0.49[Formula: see text]eV (2.17[Formula: see text]eV), 0.72[Formula: see text]eV (2.28[Formula: see text]eV) and 0.96[Formula: see text]eV (2.22[Formula: see text]eV) for NaCaNO, NaSrNO and NaBaNO quaternary half-Heusler alloys, respectively. Analysis of the density of states and the spin charge density of these quaternary alloys indicates that their magnetic moments mainly originate from the strong spin-polarization of 2[Formula: see text] states of N atoms and O atoms.
Published: 2020

8. The PLATO Solar-like Light-curve Simulator A tool to generate realistic stellar light-curves with instrumental effects representative of the PLATO mission

Author: K. Belkacem, Martin Pertenais, Daniel R. Reese, V. Marchiori, R. Samadi, Anko Börner, Sébastien Deheuvels, J. J. Green, E. Grolleau, A. Deru, Benoit Mosser, Alexis M. S. Smith, Yveline Lebreton, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), University of São Paulo (USP), German Aerospace Center (DLR), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Etudes Spatiales - Direction Des Lanceurs. (CNES), CNES, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Universidade de São Paulo = University of São Paulo (USP), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Extrasolare Planeten und Atmosphären, Weltrauminstrumente, FOS: Physical sciences, techniques: image processing, Context (language use), asteroseismology, 01 natural sciences, Asteroseismology, methods: numerical, techniques image processing, techniques: photometric, Planet, 0103 physical sciences, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Simulation, Echtzeit-Datenprozessierung, Physics, [PHYS]Physics [physics], Pixel, 010308 nuclear & particles physics, Microscanning, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], techniques photometric, Photometry (astronomy), Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Parametric model, stars: oscillations, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, methods numerical, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], stars oscillations
Abstract: The 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 PLATO Solar-like Light-curve Simulator (PSLS) in order to generate light-curves representative of typical PLATO targets, i.e. showing simultaneously solar-like oscillations, stellar granulation, and magnetic activity. At the same time, PSLS also aims at mimicking in a realistic way the random noise and the systematic errors representative of the PLATO multi-telescope concept. To quantify the instrumental systematic errors, we performed a series of simulations at pixel level that include various relevant sources of perturbations expected for PLATO. From the simulated pixels, we extract the photometry as planned on-board. The simulated light-curves are then corrected for instrumental effects using the instrument Point Spread Functions reconstructed on the basis of a microscanning technique that will be operated during the in-flight calibration phases. These corrected light-curves are then fitted by a parametric model, which we incorporated in PSLS. We show that the instrumental systematic errors dominate the signal only at frequencies below 20muHz and are found to mainly depend on stellar magnitude and on the detector charge transfer inefficiency. To illustrate how realistic our simulator is, we compared its predictions with observations made by Kepler on three typical targets and found a good qualitative agreement with the observations. PSLS reproduces the main properties of expected PLATO light-curves. Its speed of execution and its inclusion of relevant stellar signals as well as sources of noises representative of the PLATO cameras make it an indispensable tool for the scientific preparation of the PLATO mission., 19 pages, 16 figures, Astronomy & Astrophysics (in press)
Published: 2019

9. Seismic characterization of red giants going through the helium-core flash

Author: K. Belkacem, S. Deheuvels, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Convection, chemistry.chemical_element, FOS: Physical sciences, Astrophysics, 01 natural sciences, Spectral line, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, stars: oscillations (including pulsations), 010303 astronomy & astrophysics, Stellar evolution, ComputingMilieux_MISCELLANEOUS, Helium, Solar and Stellar Astrophysics (astro-ph.SR), [PHYS]Physics [physics], Physics, 010308 nuclear & particles physics, Oscillation, Astronomy and Astrophysics, Core (optical fiber), Stars, Astrophysics - Solar and Stellar Astrophysics, chemistry, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: First-ascent red giants with masses below about $2\,M_\odot$ ignite helium in their degenerate core as a flash. Stellar evolution codes predict that the He flash consists of a series of consecutive subflashes. The detection of mixed modes in red giants from space missions CoRoT and Kepler has opened new opportunities to search for stars in this evolution stage. During a subflash, the He burning shell is convective, which splits the cavity of gravity modes in two. We here investigate how this additional cavity modifies the oscillation spectrum of the star. We calculate the asymptotic mode frequencies of stellar models going through a He subflash using the JWKB approximation. To predict the detectability of the modes, we estimate their expected heights, taking into account the effects of radiative damping in the core. Our results are then compared to the oscillation spectra obtained by calculating numerically the mode frequencies during a He subflash. We show that during a He subflash, the detectable oscillation spectrum mainly consists of modes trapped in the acoustic cavity and in the outer g-mode cavity. The spectrum should thus resemble that of a core-helium-burning giant. However, we find a list of clear, detectable features that could enable us to identify red giants passing through a He subflash. In particular, during a He subflash, several modes that are trapped in the innermost g-mode cavity are expected to be detectable. We show that these modes could be identified by their frequencies or by their rotational splittings. Other features, such as the measured period spacing of gravity modes or the location of the H-burning shell within the g-mode cavity could also be used to identify stars going through a He subflash. The features derived in this study can now be searched for in the large datasets provided by the CoRoT and Kepler missions., Comment: 25 pages, 20 figures, accepted in A&A
Published: 2018

10. A non-local mixing-length theory able to compute core overshooting

Author: K. Belkacem, M. Gabriel, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Convection, Physics, [PHYS]Physics [physics], 010308 nuclear & particles physics, Differential equation, Computation, FOS: Physical sciences, Astronomy and Astrophysics, Reynolds stress, Astrophysics, 01 natural sciences, Physics::Fluid Dynamics, Temperature gradient, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Mixing length model, Stellar physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Statistical physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Free parameter
Abstract: Turbulent convection is certainly one of the most important and thorny issues in stellar physics. Our deficient knowledge of this crucial physical process introduces a fairly large uncertainty concerning the internal structure and evolution of stars. A striking example is overshoot at the edge of convective cores. Indeed, nearly all stellar evolutionary codes treat the overshooting zones in a very approximative way that considers both its extent and the profile of the temperature gradient as free parameters. There are only a few sophisticated theories of stellar convection such as Reynolds stress approaches, but they also require the adjustment of a non-negligible number of free parameters. We present here a theory, based on the plume theory as well as on the mean-field equations, but without relying on the usual Taylor's closure hypothesis. It leads us to a set of eight differential equations plus a few algebraic ones. Our theory is essentially a non-mixing length theory. It enables us to compute the temperature gradient in a shrinking convective core and its overshooting zone. The case of an expanding convective core is also discussed, though more briefly. Numerical simulations have quickly improved during recent years and enabling us to foresee that they will probably soon provide a model of convection adapted to the computation of 1D stellar models., Accepted in A&A, 17 pages
Published: 2018

11. ASTEROSEISMOLOGY OF EVOLVED STARS WITH KEPLER : A NEW WAY TO CONSTRAIN STELLAR INTERIORS USING MODE INERTIAS

Author: R. Samadi, Rita Ventura, Rafael A. García, Othman Benomar, B. Mosser, M. P. Di Mauro, Dennis Stello, Timothy R. Bedding, K. Belkacem, M. J. Goupil, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), School of Physics [UNSW Sydney] (UNSW), University of New South Wales [Sydney] (UNSW), INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), Institut de Physique du Globe de Paris, Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), and Institut de Physique du Globe de Paris (IPG Paris)
Subjects: oscillations [stars], Red giant, stars: interiors, 01 natural sciences, Kepler, Asteroseismology, 0103 physical sciences, data analysis [methods], Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Stellar evolution, Astrophysics::Galaxy Astrophysics, Physics, interiors [stars], [PHYS]Physics [physics], 010308 nuclear & particles physics, Subgiant, Mode (statistics), Astronomy, Astronomy and Astrophysics, methods: data analysis, Stars, Subject headings: stars: oscillations, Space and Planetary Science, Asteroid, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; Asteroseismology of evolved solar-like stars is experiencing a growing interest due to the wealth of observational data from space-borne instruments such as the CoRoT and Kepler spacecraft. In particular, the recent detection of mixed modes, which probe both the innermost and uppermost layers of stars, paves the way for inferring the internal structure of stars along their evolution through the subgiant and red giant phases. Mixed modes can also place stringent constraints on the physics of such stars and on their global properties (mass, age, etc...). Here, using two Kepler stars (KIC 4351319 and KIC 6442183), we demonstrate that measurements of mixed mode characteristics allow us to estimate the mode inertias, providing a new and additional diagnostics on the mode trapping and subsequently on the internal structure of evolved stars. We however stress that the accuracy may be sensitive to non-adiabatic effects.
Published: 2014

12. Oscillation mode linewidths and heights of 23 main-sequence stars observed by Kepler

Author: Othman Benomar, Tiago L. Campante, H. M. Antia, K. Belkacem, Günter Houdek, William J. Chaplin, C. Régulo, T. Appourchaux, Rasmus Handberg, Guy R. Davies, Rafael A. García, Rachel Howe, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), European Project: 267864,EC:FP7:ERC,ERC-2010-AdG_20100224,ASTERISK(2011), European Project: 269194,EC:FP7:PEOPLE,FP7-PEOPLE-2010-IRSES,ASK(2011), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)
Subjects: 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Astrophysics, asteroseismology, stars: interiors, 01 natural sciences, Asteroseismology, Spectral line, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, data analysis [Methods], 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Physics, Oscillation, Mode (statistics), interiors [Stars], Astronomy and Astrophysics, Effective temperature, methods: data analysis, Stars, Amplitude, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Main sequence
Abstract: Solar-like oscillations have been observed by Kepler and CoRoT in many solar-type stars, thereby providing a way to probe the stars using asteroseismology. We provide the mode linewidths and mode heights of the oscillations of various stars as a function of frequency and of effective temperature. We used a time series of nearly two years of data for each star. The 23 stars observed belong to the simple or F-like category. The power spectra of the 23 main-sequence stars were analysed using both maximum likelihood estimators and Bayesian estimators, providing individual mode characteristics such as frequencies, linewidths, and mode heights. We study the source of systematic errors in the mode linewidths and mode heights, and we present a way to correct these errors with respect to a common reference fit. Using the correction, we could explain all sources of systematic errors, which could be reduced to less than $\pm$15% for mode linewidths and heights, and less than $\pm$5% for amplitude, when compared to the reference fit. The effect of a different estimated stellar background and a different estimated splitting will provide frequency-dependent systematic errors that might affect the comparison with theoretical mode linewidth and mode height, therefore affecting the understanding of the physical nature of these parameters. All other sources of relative systematic errors are less dependent upon frequency. We also provide the dependence of the so-called linewidth dip, in the middle of the observed frequency range, as a function of effective temperature. We show that the depth of the dip decreases with increasing effective temperature. The dependence of the dip on effective temperature may imply that the mixing length parameter $\alpha$ or the convective flux may increase with effective temperature., Comment: Accepted by A&A, 38 pages, 35 figures, 26 tables
Published: 2014

13. Oscillation mode linewidths and heights of 23 main-sequence stars observed byKepler(Corrigendum)

Author: Tiago L. Campante, K. Belkacem, Rasmus Handberg, Rachel Howe, Rafael A. García, William J. Chaplin, Guy R. Davies, Othman Benomar, G. Houdek, Clara Régulo, T. Appourchaux, H. M. Antia, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Aarhus], Aarhus University [Aarhus], National Solar Observatory [Tucson] (NSO/Tucson), Association of Universities for Research in Astronomy (AURA)-National Science Foundation [Arlington] (NSF), Departamento de Astrofísica [La laguna], Universidad de La Laguna [Tenerife - SP] (ULL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Astronomy [Vienna], University of Vienna [Vienna], Visio per computador i robotica (VICOROB), Universitat de Girona (UdG), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), and National Science Foundation [Arlington] (NSF)-Association of Universities for Research in Astronomy (AURA)
Subjects: interiors [stars], [PHYS]Physics [physics], Physics, 010504 meteorology & atmospheric sciences, Oscillation, Mode (statistics), Astronomy, Astronomy and Astrophysics, asteroseismology, Astrophysics, 01 natural sciences, Kepler, Asteroseismology, Space and Planetary Science, 0103 physical sciences, data analysis [methods], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], errata, addenda, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Main sequence, 0105 earth and related environmental sciences
Abstract: International audience
Published: 2016

14. Stellar granulation as seen in disk-integrated intensity. I. Simplified theoretical modeling

Author: K. Belkacem, R. Samadi, Hans-Günter Ludwig, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Zentrum für Astronomie der Universität Heidelberg (ZAH), Universität Heidelberg [Heidelberg], Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Universität Heidelberg [Heidelberg] = Heidelberg University
Subjects: Physics, [PHYS]Physics [physics], Brightness, Ab initio, FOS: Physical sciences, Astronomy and Astrophysics, Context (language use), Astrophysics, 01 natural sciences, 010305 fluids & plasmas, Computational physics, Stars, Granulation, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Scaling, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Free parameter
Abstract: The solar granulation is known for a long time to be a surface manifestation of convection. Thanks to the current space-borne missions CoRoT and Kepler, it is now possible to observe in disk-integrated intensity the signature of this phenomena in a growing number of stars. The space-based photometric measurements show that the global brightness fluctuations and the lifetime associated with granulation obeys characteristic scaling relations. We thus aim at providing a simple theoretical modeling to reproduce these scaling relations and subsequently at inferring the physical properties of granulation properties across the HR diagram. We develop a simple 1D theoretical model that enable us to test any prescription concerning the time-correlation between granules. The input parameters of the model are extracted from 3D hydrodynamical models of the surface layers of stars, and the free parameters involved in the model are calibrated with solar observations. Two different prescriptions for representing the eddy time-correlation in the Fourier space are compared: a Lorentzian and an exponential form. Finally, we compare our theoretical prediction with a 3D radiative hydrodynamical (RHD) numerical modeling of stellar granulation (ab-initio approach). Provided that the free parameters are appropriately adjusted, our theoretical model satisfactorily reproduces the shape and the amplitude of the observed solar granulation spectrum. The best agreement is obtained with an exponential form. Furthermore, our theoretical model results in granulation spectra that consistently agree with the these calculated on the basis of the ab-initio approach with two 3D RHD models. Comparison between theoretical granulation spectra calculated with the present model and high precision photometry measurements of stellar granulation is undertaken in a companion paper., 10 pages, 2 figures, accepted for publication in A&A
Published: 2013

15. Properties of oscillation modes in subgiant stars observed by Kepler

Author: K. Belkacem, Charles A. Kuehn, Timothy R. Bedding, Benoit Mosser, S. Deheuvels, Timothy R. White, Othman Benomar, Jørgen Christensen-Dalsgaard, Dennis Stello, Rafael A. García, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Paris (OP), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), School of Physics [UNSW Sydney] (UNSW), University of New South Wales [Sydney] (UNSW), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Visio per computador i robotica (VICOROB), Universitat de Girona (UdG), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Aarhus], and Aarhus University [Aarhus]
Subjects: oscillations [stars], FOS: Physical sciences, Astrophysics, asteroseismology, 01 natural sciences, Measure (mathematics), Kepler, 0103 physical sciences, data analysis [methods], Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, [PHYS]Physics [physics], interiors [stars], 010308 nuclear & particles physics, Subgiant, Oscillation, Mode (statistics), Astronomy and Astrophysics, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Mixed 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 mode characteristics (frequency, height, width). Analyzing four subgiants stars, we present the first measure of the effect of the degree of mixture on the l=1 mixed modes characteristics. We also show that some stars have measurable l=2 mixed modes and discuss the interest of their measure to constrain the deeper layers of stars., Accepted to ApJ
Published: 2013

16. Stellar granulation as seen in disk-integrated intensity. II. Theoretical scaling relations compared with observations

Author: Elisabetta Caffau, Savita Mathur, Benoit Mosser, Hans-Günter Ludwig, Thomas Kallinger, Mikkel N. Lund, Annie Baglin, K. Belkacem, Rafael A. García, R. Samadi, Tiago L. Campante, and Guy R. Davies
Subjects: Physics, Brightness, Photosphere, 010504 meteorology & atmospheric sciences, Scale (ratio), Turbulence, Sigma, FOS: Physical sciences, Astronomy and Astrophysics, Function (mathematics), Astrophysics, 01 natural sciences, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Scaling, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract: A 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) and the root-mean-square (rms) brightness fluctuations (sigma) associated with the granulation scale as a function of the peak frequency (nu_max) of the solar-like oscillations. We aim at providing a theoretical background to the observed scaling relations based on a model developed in the companion paper. We computed for each 3D model the theoretical power density spectrum (PDS) associated with the granulation as seen in disk-integrated intensity on the basis of the theoretical model. For each PDS we derived tau_eff and sigma and compared these theoretical values with the theoretical scaling relations derived from the theoretical model and the Kepler measurements. We derive theoretical scaling relations for tau_eff and sigma, which show the same dependence on nu_max as the observed scaling relations. In addition, we show that these quantities also scale as a function of the turbulent Mach number (Ma) estimated at the photosphere. The theoretical scaling relations for tau_eff and sigma match the observations well on a global scale. Our modelling provides additional theoretical support for the observed variations of sigma and tau_eff with nu_m max. It also highlights the important role of Ma in controlling the properties of the stellar granulation. However, the observations made with Kepler on a wide variety of stars cannot confirm the dependence of our scaling relations on Ma. Measurements of the granulation background and detections of solar-like oscillations in a statistically sufficient number of cool dwarf stars will be required for confirming the dependence of the theoretical scaling relations with Ma., Comment: 12 pages, 6 figures,accepted for publication in A&A
Published: 2013
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17. Connections Between Stellar Oscillations and Turbulent Convection

Author: R. Samadi, K. Belkacem, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Etoile, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)
Subjects: Physics, Mode (statistics), Context (language use), Astrophysics, Effective temperature, Space (mathematics), Kepler, Asteroseismology, Stars, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Scaling, Astrophysics::Galaxy Astrophysics
Abstract: International audience; Since the advent of space asteroseismology, enabled by the CoRoT and Kepler space-craft, solar-like oscillations have appeared to be a common feature of low-mass stars from the main-sequence to the red-giant phases. In this context, scaling relations that relate asteroseismological quantities and stellar parameters are an essential tool in the study a large class of stars. Most of these relations concern the connection between pulsations and turbulent convection. Therefore, a deep investigation of this connection is necessary to obtain insight into the processes underlying mode driving and damping and consequently to improve our knowledge of the scaling relations. This is a key step that will permit us to perform a leap forward in our understanding of stellar interiors.
Published: 2013

18. Characterization of the power excess of solar-like oscillations in red giants with Kepler

Author: Benoit Mosser, Savita Mathur, Y. P. Elsworth, K. Belkacem, Timothy R. Bedding, Robert L. Morris, Christopher K. Middour, Rafael A. García, Daniel Huber, Elisa V. Quintana, M. J. Goupil, William J. Chaplin, Saskia Hekker, Thomas Kallinger, J. De Ridder, Dennis Stello, C. Barban, Reza Samadi, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), School of Physics and Astronomy, University of Birmingham [Birmingham], Sydney Institute for Astronomy (SIfA), The University of Sydney, Institute for Astronomy [Vienna], University of Vienna [Vienna], Space Science Institute [Boulder] (SSI), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Paris (OP), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), School of Physics [UNSW Sydney] (UNSW), University of New South Wales [Sydney] (UNSW), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Low Energy Astrophysics (API, FNWI)
Subjects: Stellar mass, Red giant, FOS: Physical sciences, Astrophysics, 01 natural sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Solar-like oscillations, 010303 astronomy & astrophysics, Scaling, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, Physics, [PHYS]Physics [physics], 010308 nuclear & particles physics, Oscillation, Mode (statistics), Astronomy and Astrophysics, Stars, Amplitude, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We 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 different methods were compared in order to validate the processes and to derive reliable output values. For consistency, a single method was then used to determine scaling relations for the relevant global asteroseismic parameters: mean mode height, mean height of the background signal superimposed on the oscillation power excess, width of the power excess, bolometric amplitude of the radial modes and visibility of non-radial modes. A method for deriving oscillation amplitudes is proposed, which relies on the complete identification of the red giant oscillation spectrum. The comparison of the different methods has shown the important role of the way the background is modelled. The convergence reached by the collaborative work enables us to derive significant results concerning the oscillation power excess. We obtain several scaling relations, and identify the influence of the stellar mass and the evolutionary status. The effect of helium burning on the red giant interior structure is confirmed: it yields a strong mass-radius relation for clump stars. We find that none of the amplitude scaling relations motivated by physical considerations predict the observed mode amplitudes of red giant stars. In parallel, the degree-dependent mode visibility exhibits important variations. Both effects seem related to the significant influence of the high mode mass of non-radial mixed modes. A family of red giants with very weak dipole modes is identified, and its properties are analyzed., Comment: Accepted in A&A
Published: 2012

19. Mixed modes in red-giant stars observed with CoRoT

Author: K. Belkacem, M. J. Goupil, Frédéric Baudin, Eric Michel, Reza Samadi, Michel Auvergne, C. Barban, Marc-Antoine Dupret, Andrea Miglio, J. De Ridder, Benoit Mosser, Y. P. Elsworth, Paul G. Beck, Josefina Montalbán, Saskia Hekker, Annie Baglin, Claude Catala, Alfred F. Noels, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Etoile, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut d'Astrophysique, Géophysique et Océanographie, Université de Liège, Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), School of Physics and Astronomy, University of Birmingham, and Low Energy Astrophysics (API, FNWI)
Subjects: Red giant, Population, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, 7. Clean energy, Gravitation, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Envelope (mathematics), education, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, education.field_of_study, 010308 nuclear & particles physics, Oscillation, Autocorrelation, Astronomy and Astrophysics, Light curve, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; Context. The CoRoT mission has provided thousands of red-giant light curves. The analysis of their solar-like oscillations allows us to characterize their stellar properties. Aims: Up to now, the global seismic parameters of the pressure modes have been unable to distinguish red-clump giants from members of the red-giant branch. As recently done with Kepler red giants, we intend to analyze and use the so-called mixed modes to determine the evolutionary status of the red giants observed with CoRoT. We also aim at deriving different seismic characteristics depending on evolution. Methods: The complete identification of the pressure eigenmodes provided by the red-giant universal oscillation pattern allows us to aim at the mixed modes surrounding the l = 1 expected eigenfrequencies. A dedicated method based on the envelope autocorrelation function is proposed to analyze their period separation. Results: We have identified the mixed-mode signature separation thanks to their pattern that is compatible with the asymptotic law of gravity modes. We have shown that, independent of any modeling, the g-mode spacings help to distinguish the evolutionary status of a red-giant star. We then report the different seismic and fundamental properties of the stars, depending on their evolutionary status. In particular, we show that high-mass stars of the secondary clump present very specific seismic properties. We emphasize that stars belonging to the clump were affected by significant mass loss. We also note significant population and/or evolution differences in the different fields observed by CoRoT.
Published: 2011

20. Amplitudes of Solar Gravity Modes

Author: K. Belkacem, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Etoile, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)
Subjects: Turbulent convection, Physics, Gravity (chemistry), Amplitude, Turbulent viscosity, Track (disk drive), Physics::Space Physics, Mode (statistics), Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, Mechanics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Solar gravity modes are mainly trapped inside the radiative region and are then able to provide information on the properties of the central part of the Sun granulation. However, there is no consensus on the detection of solar gravity modes which remains a major challenge. In this paper, we discuss the underlying driving and damping processes of solar $g$ modes, and review the quantitative estimates of their amplitudes. This issue is important since a theoretical determination of mode amplitudes may help to design the track for gravity modes.
Published: 2011

21. The Asteroseismic Potential of Kepler: First Results for Solar-Type Stars

Author: W. J. Chaplin, T. Appourchaux, Y. Elsworth, R. A. García, G. Houdek, C. Karoff, T. S. Metcalfe, J. Molenda-Żakowicz, M. J. P. F. G. Monteiro, M. J. Thompson, T. M. Brown, J. Christensen-Dalsgaard, R. L. Gilliland, H. Kjeldsen, W. J. Borucki, D. Koch, J. M. Jenkins, J. Ballot, S. Basu, M. Bazot, T. R. Bedding, O. Benomar, A. Bonanno, I. M. Brandão, H. Bruntt, T. L. Campante, O. L. Creevey, M. P. Di Mauro, G. Doğan, S. Dreizler, P. Eggenberger, L. Esch, S. T. Fletcher, S. Frandsen, N. Gai, P. Gaulme, R. Handberg, S. Hekker, R. Howe, D. Huber, S. G. Korzennik, J. C. Lebrun, S. Leccia, M. Martic, S. Mathur, B. Mosser, R. New, P.-O. Quirion, C. Régulo, I. W. Roxburgh, D. Salabert, J. Schou, S. G. Sousa, D. Stello, G. A. Verner, T. Arentoft, C. Barban, K. Belkacem, S. Benatti, K. Biazzo, P. Boumier, P. A. Bradley, A.-M. Broomhall, D. L. Buzasi, R. U. Claudi, M. S. Cunha, F. D'Antona, S. Deheuvels, A. Derekas, A. García Hernández, M. S. Giampapa, M. J. Goupil, M. Gruberbauer, J. A. Guzik, S. J. Hale, M. J. Ireland, L. L. Kiss, I. N. Kitiashvili, K. Kolenberg, H. Korhonen, A. G. Kosovichev, F. Kupka, Y. Lebreton, B. Leroy, H.-G. Ludwig, S. Mathis, E. Michel, A. Miglio, J. Montalbán, A. Moya, A. Noels, R. W. Noyes, P. L. Pallé, L. Piau, H. L. Preston, T. Roca Cortés, M. Roth, K. H. Sato, J. Schmitt, A. M. Serenelli, V. Silva Aguirre, I. R. Stevens, J. C. Suárez, M. D. Suran, R. Trampedach, S. Turck-Chièze, K. Uytterhoeven, R. Ventura, P. A. Wilson, School of Physics and Astronomy [Birmingham], University of Birmingham [Birmingham], Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institute for Astronomy [Vienna], University of Vienna [Vienna], High Altitude Observatory (HAO), National Center for Atmospheric Research [Boulder] (NCAR), Astronomical Institute [Wroclaw], University of Wrocław [Poland] (UWr), Centro de Astrofísica da Universidade do Porto (CAUP), Universidade do Porto, School of Mathematics and Statistics [Sheffield] (SoMaS), University of Sheffield [Sheffield], Las Cumbres Observatory (LCO), Department of Physics and Astronomy [Aarhus], Aarhus University [Aarhus], Space Telescope Science Institute (STSci), NASA Ames Research Center (ARC), SETI Institute, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Department of Astronomy [New Haven], Yale University [New Haven], Sydney Institute for Astronomy (SIfA), The University of Sydney, INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), Observatoire de Paris, Université Paris sciences et lettres (PSL), Departamento de Astrofísica [La laguna], Universidad de La Laguna [Tenerife - SP] (ULL), Instituto de Astrofisica de Canarias (IAC), Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Materials and Engineering Research Institute [Sheffield] (MERI), Sheffield Hallam University, Beijing Normal University (BNU), National Solar Observatory [Tucson] (NSO/Tucson), National Science Foundation [Arlington] (NSF)-Association of Universities for Research in Astronomy (AURA), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), INAF - Osservatorio Astronomico di Capodimonte (OAC), Indian Institute of Astrophysics (IIA), Observatoire de Paris - Site de Paris (OP), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Canadian Space Agency (CSA), Astronomy Unit [London] (AU), Queen Mary University of London (QMUL), Hansen Experimental Physics Lab [Stanford] (HEPL), Stanford University, Département d'astrophysique, Géophysique et Océanographie (AGO), Université de Liège, Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), Universita degli Studi di Padova, INAF - Osservatorio Astrofisico di Arcetri (OAA), Los Alamos National Laboratory (LANL), Eureka Scientific, INAF - Osservatorio Astronomico di Padova (OAPD), INAF - Osservatorio Astronomico di Roma (OAR), Konkoly Observatory, Research Centre for Astronomy and Earth Sciences [Budapest], Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Department of Astronomy and Physics [Halifax], Saint Mary's University [Halifax], Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut d'Astrophysique et de Géophysique [Liège], Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Universidade do Porto = University of Porto, Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Georg-August-University = Georg-August-Universität Göttingen, Université de Genève = University of Geneva (UNIGE), Harvard University-Smithsonian Institution, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Università degli Studi di Padova = University of Padua (Unipd), and Faculdade de Ciências
Subjects: oscillations [stars], Física [Ciências exactas e naturais], FOS: Physical sciences, Astrophysics, Type (model theory), Star (graph theory), stars: interiors, 01 natural sciences, Kepler, Spectral line, Physical sciences [Natural sciences], Astrophysics, Astronomy, Physical sciences, Physical sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrofísica, Astronomia, Ciências Físicas, Física, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, interiors [stars], 010308 nuclear & particles physics, Oscillation, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stars: late-type, Astronomy and Astrophysics, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, late-type [stars], Astrophysics::Earth and Planetary Astrophysics, stars: oscillations
Abstract: We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5d of science operations, reveal high signal-to-noise solar-like oscillation spectra in all three stars: About 20 modes of oscillation may be clearly distinguished in each star. We discuss the appearance of the oscillation spectra, use the frequencies and frequency separations to provide first results on the radii, masses and ages of the stars, and comment in the light of these results on prospects for inference on other solar-type stars that Kepler will observe., Comment: 16 pages, 3 figures, 1 table; now accepted for publication in ApJ Letters
Published: 2010

22. Stochastic excitation of gravity modes in massive main-sequence stars

Author: R. Samadi, K. Belkacem, M. J. Goupil, M.-A. Dupret, A. S. Brun, and A. Noels
Published: 2009

23. CoRot observations of active giants: preliminary results

Author: P. Gondoin, M. Fridlund, M. J. Goupil, F. Baudin, R. Samadi, C. Barban, K. Belkacem, T. Corbard, M. A. Dupret, B. Foing, R. den Hartog, Y. Lebreton, J. Lochard, P. Mathias, E. Michel, P. Morel, A. Moya, A. Palacios, J. P. Zahn, Eric Stempels, Geneva Observatory, University of Geneva [Switzerland], Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Observatoire de Paris - Site de Paris (OP), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Space Sciences, Technologies and Astrophysics Research Institute (STAR), Université de Liège, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Airbus Defence and Space [Toulouse], Laboratoire Hippolyte Fizeau (FIZEAU), DAM Île-de-France (DAM/DIF), Direction des Applications Militaires (DAM), Institut Cavanilles de Biodiversitat i Biologia Evolutiva (ICBiBE), Universitat de València (UV), Institute of Environmental Assessment and Water Research (IDAEA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Department of Physics and Astronomy [Uppsala], Uppsala University, Université de Genève = University of Geneva (UNIGE), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Rotation period, Physics, 13. Climate action, Star formation, Stellar rotation, Astronomy, Astrophysics, Effective temperature, Rotation, Giant star, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], ComputingMilieux_MISCELLANEOUS
Abstract: We have analysed rotation modulated light‐curves of active giants observed with CoRot using spots model. Preliminary results suggest an increase of the surface spot coverage with decreasing rotation period. A maximum of the surface spot coverage seems to occur on giants with effective temperature around 5100 K. Confirmation and interpretation of these preliminary results require groundbased follow‐up observations to measure activity indicators, to identify binary systems, and to determine the stellar parameters and evolutionary status of the sample giants.
Published: 2008

24. A new image smoothing method based on a simple model of spatial processing in the early stages of human vision

Author: Azeddine Beghdadi and K. Belkacem-Boussaid
Subjects: business.industry, Low-pass filter, ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, Image processing, Filter (signal processing), Real image, Computer Graphics and Computer-Aided Design, Noise, Nonlinear filter, Computer vision, Artificial intelligence, business, Software, Linear filter, Smoothing, Mathematics
Abstract: The difficulty of preserving edges is central to the problem of smoothing images. The main problem is that of distinguishing between meaningful contours and noise, so that the image can be smoothed without loss of details. Substantial efforts have been devoted to solving this difficult problem, and a plethora of filtering methods have been proposed in the literature. Non-linear filters have proved to be more efficient than their linear counterparts. Here, a new nonlinear filter for noise smoothing is introduced. This filter is based on the psychophysical phenomenon of human visual contrast sensitivity. Results on real images are presented to demonstrate the validity of our approach compared to other known filtering methods.
Published: 2008

25. Low-level vision treatments inspired from human visual system

Author: Azeddine Beghdadi, K. Belkacem-Boussaid, and Abdel-Ouahab Boudraa
Subjects: Visual perception, genetic structures, Computer science, business.industry, media_common.quotation_subject, SIGNAL (programming language), eye diseases, Edge detection, Digital image, Human visual system model, Contrast (vision), Computer vision, Sensitivity (control systems), Artificial intelligence, Set (psychology), business, media_common
Abstract: A set of low-level vision treatments inspired from some knowledge of mammalian retino-cortical mechanisms is proposed. The basic idea is to exploit the contrast sensitivity response of the human visual system (HVS) and the multichannel decomposition of the visual signal in the cortex. The scope of this work is limited to nonlinear filtering, contrast enhancement and edge detection but could be extended to other image treatments.
Published: 2003

26. Edge detection using Holladay's principle

Author: Azeddine Beghdadi, H. Depoisot, and K. Belkacem-Boussaid
Subjects: Visual perception, medicine.anatomical_structure, business.industry, Human visual system model, Canny edge detector, medicine, Computer vision, Human eye, Artificial intelligence, business, Edge detection, Deriche edge detector, Mathematics
Abstract: We propose herein a new contour detection algorithm based on the human visual system. Using the proposed method, one can automatically select the thresholds that define the significant edges, such as perceived by the human eye. The threshold value is adapted to the background and surround intensities, according to criteria involved by Holladay's principle.
Published: 2002

27. Non linear smoothing method based on the just-noticeable contrast

Author: K. Belkacem-Boussaid and A. Beghdadi
Subjects: business.industry, ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, Contrast (statistics), Edge-preserving smoothing, Image enhancement, Nonlinear system, Computer vision, Artificial intelligence, business, Just noticeable, Algorithm, Smoothing, ComputingMethodologies_COMPUTERGRAPHICS, Mathematics
Abstract: The present paper provides a new smoothing method, based on psychophysical phenomena, in which the optimum smoothing parameters are automatically chosen. The method is a nonlinear one and it has some similarities with well-known morphological filters.
Published: 2002

28. [Medication error rate in the hospital setting: a pilot study at the Jury-lès-Metz Hospital Center]

Author: K, Belkacem, D J, Lepaux, and R, Oliger
Subjects: Medication Systems, Hospital, Data Interpretation, Statistical, Humans, Medication Errors, Pilot Projects, France
Abstract: Medication error rate (TEM) is seen as the performance rate of the process leading from drug prescription to drug administration. Jury-lès-Metz Psychiatric Hospital conducted a pilot study whose aim was to determine feasibility of drug error rate calculation.TEM was calculated as the number of errors divided by the number (n) of all the doses ordered. Four different steps of the process were studied with a specific rate for each step: drug prescription error rate (TEMp), drug delivery calculation error rate (TEMr), drug missing before administration rate (TEMm) and nursing error in drug preparing rate (TEMc).TEMp (n = 15,699): 1.92% [1.74-2.10], TEMr (n = 3457): 2.7% [2.2-3.2], TEMm (n = 3457): 6.9% [6.1-7.7], TEMc (n = 956): 5.9% [4.4-7.4].The research topic presented here is quite new. In spite of certain limitations, the most important point is to focus attention on four specific steps and not to limit the study to the entire process. Our pilot work demonstrates that drug errors are made and must not be neglected. The TEM is not simply the sum of specific errors because of the interactions between the underlying causes of the different types of errors, each affecting the value of specific TEMs.Before to deal with quality improvement of hospital medication process, we had to prove that drug error exists. Now, two solve the problem of medication error in our hospital, we have to observe what exactly happens and to try to multidisciplinary understand the causes leading to process defects.
Published: 2001

29. The underlying physical meaning of theνmax − νcrelation

Author: Reza Samadi, Arlette Noels, Frédéric Baudin, M. J. Goupil, Benoit Mosser, K. Belkacem, Marc-Antoine Dupret, Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Institut d'Astrophysique, Géophysique et Océanographie, Université de Liège, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Etoile, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)
Subjects: Physics, Oscillation, Perturbation (astronomy), Spectral density, Astronomy and Astrophysics, Astrophysics, Plateau (mathematics), Asteroseismology, Stars, Entropy (classical thermodynamics), Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Scaling
Abstract: International audience; Asteroseismology 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 parameters are becoming essential tools to study a rich variety of stars. However, the physical underlying mechanisms of those scaling laws are still poorly known. Our objective is to provide a theoretical basis for the scaling between the frequency of the maximum in the power spectrum (numax) of solar-like oscillations and the cut-off frequency (nuc). Using the SoHO GOLF observations together with theoretical considerations, we first confirm that the maximum of the height in oscillation power spectrum is determined by the so-called plateau of the damping rates. The physical origin of the plateau can be traced to the destabilizing effect of the Lagrangian perturbation of entropy in the upper-most layers, which becomes important when the modal period and the local thermal relaxation time-scale are comparable. Based on this analysis, we then find a linear relation between numax and nuc, with a coefficient that depends on the ratio of the Mach number of the exciting turbulence to the third power to the mixing-length parameter.
Published: 2011

30. Solar-like oscillations in massive main-sequence stars

Author: Arlette Noels, K. Belkacem, and Marc-Antoine Dupret
Subjects: Physics, Convection, Opacity, Computation, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Convection zone, Space and Planetary Science, Excited state, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Solar-like oscillations, Solar and Stellar Astrophysics (astro-ph.SR), Main sequence
Abstract: Motivated by the recent detection of stochastically excited modes in the massive star V1449 Aql (Belkacem et al., 2009b), already known to be a $\beta$ Cephei, we theoretically investigate the driving by turbulent convection. By using a full non-adiabatic computation of the damping rates, together with a computation of the energy injection rates, we provide an estimate of the amplitudes of modes excited by both the convective region induced by the iron opacity bump and the convective core. Despite uncertainties in the dynamical properties of such convective regions, we demonstrate that both are able to efficiently excite $p$ modes above the CoRoT observational threshold and the solar amplitudes. In addition, we emphasise the potential asteroseismic diagnostics provided by each convective region, which we hope will help to identify the one responsible for solar-like oscillations, and to give constraints on this convective zone. A forthcoming work will be dedicated to an extended investigation of the likelihood of solar-like oscillations across the Hertzsprung-Russell diagram., Comment: 9 pages, 14 figures, accepter in A&A
Published: 2010

31. Asymmetry of Line Profiles of Stellar Oscillations Measured by Kepler for Ensembles of Solar-like Oscillators: Impact on Mode Frequencies and Dependence on Effective Temperature.

Author: O. Benomar, Mjo. Goupil, K. Belkacem, T. Appourchaux, M. B. Nielsen, M. Bazot, L. Gizon, S. Hanasoge, K. R. Sreenivasan, and B. Marchand
Subjects: STELLAR oscillations, LORENTZIAN function, HR diagrams, SUPERPOSITION principle (Physics)
Abstract: Oscillation properties are usually measured by fitting symmetric Lorentzian profiles to the power spectra of Sun-like stars. However, the line profiles of solar oscillations have been observed to be asymmetrical for the Sun. The physical origin of this line asymmetry is not fully understood; though, it should depend on the depth dependence of the source of wave excitation (convective turbulence) and details of the observable (velocity or intensity). For oscillations of the Sun, it has been shown that neglecting the asymmetry leads to systematic errors in the frequency determination. This could subsequently affect the results of seismic inferences of the solar internal structure. Using light curves from the Kepler spacecraft, we have measured mode asymmetries in 43 stars. We confirm that neglecting the asymmetry leads to systematic errors that can exceed the 1σ confidence intervals for seismic observations longer than one year. Therefore, the application of an asymmetric Lorentzian profile should be favored to improve the accuracy of the internal stellar structure and stellar fundamental parameters. We also show that the asymmetry changes sign between cool Sun-like stars and hotter stars. This provides the best constraints to date on the location of the excitation sources across the Hertzsprung–Russel diagram. [ABSTRACT FROM AUTHOR]
Published: 2018
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32. Surface convection: from the Sun to red giant stars

Author: Piau, Laurent, Kervella, P., Dib, S., Hauschildt, P., HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Imperial College of Science, Technology and Medicine, Imperial College London, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, Haute résolution angulaire en astrophysique, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Cardon, Catherine, and G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud
Subjects: Surface convection, [PHYS.ASTR.SR] Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Sun, FOS: Physical sciences, Red giant stars, Astrophysics::Cosmology and Extragalactic Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Interferometry, Astrophysics - Solar and Stellar Astrophysics, [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract: We check how the change in surface conditions between the Sun and red giant branch stars changes the characteristic surface convection length scale to be used in models. We investigate the question in the case of the mixing length theory and of the phenomenology of full spectrum of turbulence. For the observational part, we rely on independent measurements of effective temperatures and interferometric radii of nearby red giants. We find that the local red giant branch cannot be explained taking into account the solar calibrated convective length scale., In the proceedings of the French Astronomical Society meeting SF2A 2011
Published: 2011

33. The physical parameters of the low-mass multiple system LHS1070 from Spectral synthesis analysis

Author: Rajpurohit, A. S., Reylé, C., Schultheis, M., Leinert, C., Allard, F., Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), G. Alecian, K. Belkacem, R. Samadi, D. Valls-Gabaud, eds., Debray, Bernard, G. Alecian, K. Belkacem, R. Samadi, D. Valls-Gabaud, eds., Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2011

34. Simulations of the solar atmosphere and solar limbs

Author: Piau, Laurent, Stein, R. F., Melo, S., Turck-Chièze, S., Thuillier, Gérard, Hauchecorne, Alain, HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [East Lansing], Michigan State University [East Lansing], Michigan State University System-Michigan State University System, Canadian Space Agency (CSA), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), STRATO - LATMOS, G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, Cardon, Catherine, and G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud
Subjects: [PHYS.ASTR.SR] Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Solar atmosphere, [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Limb darkening, Magnetic activity, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Simulation
Abstract: International audience; We perform simulations of the solar atmosphere either using the 1D hydrostatic code Atlas12 or the 3D (magneto)hydrodynamic code Stagger. The former numerical tool relies on a phenomenology of convection whereas the later one addresses the surface convection directly and accounts for its dynamical effects. Once the average atmosphere stratification is obtained it is used to perform radiative transfer at speficic wavelengths in order to compute the solar limb darkening. We report a ≈ 60 mas shift between inflection point positions of limb profiles computed from 1D and 3D models. This is due to turbulent support present in 3D simulations but not 1D. We further report a slight decrease of the turbulent support when a moderate magnetic field is included in the simulation which suggests that the solar radius should be anti-correlated with the solar activity cycle.
Published: 2011

35. Measuring the absolute non-gravitational acceleration of a spacecraft: goals, devices, methods, performances

Author: Lenoir, Benjamin, Christophe, Bruno, Reynaud, Serge, ONERA - The French Aerospace Lab [Châtillon], ONERA-Université Paris Saclay (COmUE), Laboratoire Kastler Brossel (LKB (Jussieu)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), G. Alecian, K. Belkacem, R. Samadi, and D. Valls-Gabaud, Lenoir, Benjamin, G. Alecian, K. Belkacem, R. Samadi, and D. Valls-Gabaud, Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics - Instrumentation and Detectors, [PHYS.GRQC] Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], FOS: Physical sciences, Instrumentation and Detectors (physics.ins-det), General Relativity and Quantum Cosmology (gr-qc), Space Physics (physics.space-ph), General Relativity and Quantum Cosmology, Physics - Space Physics, [PHYS.PHYS.PHYS-INS-DET] Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Physics - Data Analysis, Statistics and Probability, Physics::Space Physics, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Data Analysis, Statistics and Probability (physics.data-an)
Abstract: Space provides unique opportunities to test gravitation. By using an interplanetary spacecraft as a test mass, it is possible to test General Relativity at the Solar System distance scale. This requires to compute accurately the trajectory of the spacecraft, a process which relies on radio tracking and is limited by the uncertainty on the spacecraft non-gravitational acceleration. The Gravity Advanced Package (GAP) is designed to measure the non-gravitational acceleration without bias. It is composed of an electrostatic accelerometer supplemented by a rotating stage. This article presents the instrument and its performances, and describes the method to make unbiased measurements. Finally, it addresses briefly the improvement brought by the instrument as far as orbit reconstruction is concerned., Proceedings SF2A 2011 (Paris, France - June 2010), 5 pages
Published: 2011

36. Main lessons from GOLF/SOHO instrument on dynamics of the radiative zone, fundamental physics and energetics

Author: Turck-Chièze, S., Rafael A. García, Piau, L., Couvidat, S., Cardon, Catherine, G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Hansen Experimental Physics Lab [Stanford] (HEPL), Stanford University, G. Alecian, K. Belkacem, and R. Samadi and D. Valls-Gabaud
Subjects: Stellar modelling, Sound speed, [PHYS.ASTR.SR] Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Physics::Space Physics, Helioseismology, [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Solar and Stellar Astrophysics, Internal rotation, Astrophysics::Earth and Planetary Astrophysics, Neutrinos, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], WIMPS
Abstract: International audience; The GOLF instrument aboard SoHO has reached its main objectives and reveals its power to constrain fundamental physics, energetics and dynamics of the radiative zone. The Standard Solar Model (SSM) is no more su cient to interpret all the seismic observations of the solar radiative zone. We confront the main results of GOLF to models beyond the SSM assumptions. We discuss the missing processes and quantify some of them to build a more realistic view of our star. Present works on GOLF instrument are now turned on its capability to follow the solar activity and on a tentative to detect more gravity modes. All the results are useful for solar-like stars observed by COROT and KEPLER.
Published: 2011

37. Étude du couplage entre convection turbulente et oscillations de type solaire

Author: Philidet, Jordan, Observatoire de Paris, Université Paris sciences et lettres (PSL), and M.-J. Goupil, K. Belkacem
Subjects: Turbulence, Sismologie, Physique stellaire, Stellar physics, Convection, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Seismology
Abstract: Asteroseismology has revolutionised our understanding of stellar interiors, through the observations of oscillations on the surface of stars. In solar-like oscillators, which exhibit a convective envelope, the turbulent motions caused by convection have a substantial impact on the properties of the acoustic modes, whether on their frequencies or their amplitude. This impact results from a turbulence/oscillation coupling, which must therefore be understood and realistically modelled in order to allow for accurate seismic diagnosis. In turn, this coupling offers a way to constrain the little-understood properties of convection using the observed acoustic mode properties. This last point forms the overarching motivation behind the work presented in this thesis.The first part of this thesis focuses on the asymmetry displayed by the line profiles of solar-like oscillations, which carries the signature of the localisation of the driving source close to the surface of the star. In this context, I developed a formalism designed to give quantitative predictions for solar-like mode asymmetry, and to directly relate the observed asymmetries to the underlying properties of turbulence in this region. Applying this formalism to the solar case allowed me to successfully reproduce the observations throughout the entire p-mode spectrum for spectroscopic measurements, as well as in the low-frequency part of the spectrum for photometric measurements. In particular, it led me to the determination of the sign of the asymmetry depending on the stochastic excitation occurring above or beneath the photosphere. It also allowed be to shed a new light upon the issue of asymmetry reversal between the velocity and intensity measurements.In a second part, I interested myself with the modelling of the turbulence/oscillation modelling more generally. I investigated Lagrangian stochastic models of turbulence as an alternative way, compared to more traditional approaches, to model the coupling between turbulent convection and solar-like oscillations. First, a linear perturbative treatment of this class of models led me to establish a wave equation which, by construction, contains a stochastic part representing the impact of turbulence on the modes. This stochastic wave equation includes the effect of turbulence, and therefore the effect of the coupling with oscillations, in a consistent way, while allowing for the introduction of a realistic model of turbulence, taking into account the large range of time and spatial scales characterising stellar turbulent convection. This formalism then allowed me to simultaneously build physically-grounded prescriptions for the driving and damping of the modes, as well as for the modal part of the surface effects. In parallel, I developed a more direct numerical implementation of Lagrangian stochastic models, which allows, in conjunction with my analytical formalism, to explore the impact of the physical parameters of turbulent convection on the observed properties of the solar-like modes. I propose a test case where exact analytical results can be derived, and the close agreement reached between those and numerical results validates this implementation.; L’astérosismologie a révolutionné notre compréhension des intérieurs stellaires, grâce à l’observation des oscillations à la surface des étoiles. En ce qui concerne les oscillateurs de type solaire, qui possèdent une enveloppe convective, les mouvements turbulents dus à la convection ont un impact important sur les propriétés des modes acoustiques, tant du point de vue de leur fréquence que de leur amplitude. Cet impact résulte d’un couplage entre convection et oscillations, qui doit donc être compris et correctement modélisé pour permettre des diagnostics sismiques fiables dans ces étoiles. En retour, ce couplage offre l’opportunité d’utiliser les propriétés observées des modes pour contraindre la convection stellaire – dont les propriétés restent encore relativement mal comprises à ce jour. C’est ce dernier point qui constitue la motivation sous-tendant le travail présenté dans cette thèse.La première partie de cette thèse se concentre sur l’asymétrie exhibée par les profils des modes dans le spectre des oscillateurs de type solaire, qui porte la signature de la localisation de leur source d’excitation proche de la surface de l’étoile. Dans ce contexte, j’ai développé un formalisme conçu pour fournir des prédictions quantitatives concernant ces asymétries, mais également pour relier directement les asymétries observées aux propriétés sous-jacentes de la convection turbulente dans cette région. L’application de ce formalisme au cas du Soleil m’a permis de reproduire les observations à travers tout le spectre des modes acoustiques pour les mesures spectroscopiques, ainsi que pour les modes acoustiques de basse fréquence pour les mesures photométriques. En particulier, elle m’a permis de déterminer la dépendance du signe de l’asymétrie en fonction de la position de la source relativement à la photosphère, ainsi que d’apporter un éclairage nouveau sur la question de l’inversion d’asymétrie entre les observations effectuées en vitesse et en intensité.Dans une seconde partie, je me suis penché sur la question de la modélisation du couplage turbulence/oscillation de manière plus générale. J’y examine les modèles de turbulence Lagrangiens stochastiques en tant qu’alternative aux approches traditionnelles pour le traitement du couplage entre convection turbulente et oscillations de type solaire. Premièrement, un traitement perturbatif linéaire de ce type de modèle m’a permis d’exhiber une équation d’onde possédant, par construction, un caractère stochastique représentant l’impact de la turbulence sur les modes. Cette équation d’onde stochastique présente l’avantage d’inclure dès le début l’effet de la turbulence, et par suite celui du couplage, de manière cohérente, tout en permettant l’introduction d’un modèle de turbulence réaliste, et prenant en compte le large éventail d’échelles temporelles et spatiales caractérisant la convection turbulente stellaire. Ce formalisme m’a ensuite permis de construire une prescription simultanée, sur la base de relations de fermeture physique, pour le taux d’excitation et d’amortissement des modes acoustiques, mais également pour la partie modale des effets de surface. En parallèle, j’ai développé une implémentation numérique plus directe des modèles Lagrangiens stochastiques, qui permet, en conjonction avec mon formalisme analytique, d’explorer l’impact des paramètres physiques contrôlant la convection turbulente sur les propriétés observées des modes de type solaire. Le très bon accord obtenu en comparant les résultats numériques à un cas test dans le cadre duquel des résultats analytiques exacts peuvent être établis m’a permis de valider cette implémentation.
Published: 2021

38. Calibration of the Gaia RVS from ground-based observations of candidate standard stars

Author: Chemin, L., Soubiran, C., Crifo, Françoise, Jasniewicz, Gérard, Katz, David, Hestroffer, Daniel, Udry, Stéphane, sSE 2011, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB), M2A 2011, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Groupe de Recherche en Astronomie et Astrophysique du Languedoc (GRAAL), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Eds.: G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), and Université de Genève = University of Geneva (UNIGE)
Subjects: [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Techniques: radial velocities, Astrophysics::Instrumentation and Methods for Astrophysics, Galaxy : kinematics and dynamics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics::Solar and Stellar Astrophysics, Minor planets, Galaxy : structure, Astrophysics::Earth and Planetary Astrophysics, Surveys, Astrophysics::Galaxy Astrophysics, asteroids: general, Stars: kinematics and dynamics
Abstract: International audience; The Radial Velocity Spectrometer (RVS) on board of Gaia will perform a large spectroscopic survey to determine the radial velocities of some 1.5 × 10^8 stars. We present the status of ground-based observations of a sample of 1420 candidate standard stars designed to calibrate the RVS. Each candidate star has to be observed several times before Gaia launch (and at least once during the mission) to ensure that its radial velocity remains stable during the whole mission. Observations are performed with the high-resolution spectrographs SOPHIE, NARVAL and CORALIE, completed with archival data of the ELODIE and HARPS instruments. The analysis shows that about 7% of the current catalogue exhibits variations larger than the adopted threshold of 300 m s^{-1}. Consequently, those stars should be rejected as reference targets, due to the expected accuracy of the Gaia RVS. Emphasis is also put here on our observations of bright asteroids to calibrate the ground-based velocities by a direct comparison with celestial mechanics. It is shown that the radial velocity zero points of SOPHIE, NARVAL and CORALIE are consistent with each other, within the uncertainties. Despite some scatter, their temporal variations remain small with respect to our adopted stability criterion.
Published: 2011

39. Orbit of potentially hazardous asteroids using Gaia and ground-based observations

Author: Bancelin, David, Hestroffer, Daniel, Thuillot, William, Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Eds.: G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)
Subjects: b-plane, orbit determination, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Physics::Space Physics, Gaia mission, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], astrometry, Astrophysics::Earth and Planetary Astrophysics, Potentially Hazardous Asteroids
Abstract: International audience; Potentially Hazardous Asteroids (PHAs) are Near Earth Asteroids characterized by a Minimum Orbital Intersection Distance (MOID) with Earth less to 0,05 A.U and an absolute magnitude H
Published: 2011

40. Simulating the Galaxy and applications to the preparation of the Gaia mission

Author: Robin, A. C., Reylé, C., Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), G. Alecian, K. Belkacem, R. Samadi, D. Valls-Gabaud, and eds.
Subjects: [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2011

41. Updated orbit of Apophis with recent observations

Author: Bancelin, David, Colas, François, Thuillot, William, Hestroffer, Daniel, Assafin, Marcelo, Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Observatório do Valongo/UFRJ [Rio de Janeiro], Universidade Federal do Rio de Janeiro (UFRJ), Eds.: G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)
Subjects: b-plane, PHAs, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], keyhole, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], astrometry, ellipse uncertainty, Apophis
Abstract: International audience; Asteroid Apophis (previously designed 2004 MN4) was first discovered in June 2004. From its first observations, Apophis was revealed to be a special study case in as much as, it reached the level 4 of Torino scale with a high probability of collision in 2029. New observations eliminated all danger for 2029. But, because of a deep close encounter in 2029 (˜38000 km), the asteroid will be put on a chaotic-like orbit and some risks of collision in 2036 occur if the asteroid goes through a very small region called keyhole. Now, its orbit is quite well known and thanks to additional observations, the risk for the short term seems to disappear. But what about the long term? As far as the Earth-impact threat study is concerned, the deep 2029-close encounter is an opportunity for space missions towards Apophis. With our technologies, to deflect an asteroid, we can only act from the source. Many deflection missions were studied, from the hardest (nuclear weapons), to the softest (shadow mission). But in order to prepare such missions, we have to be sure that the asteroid is really on an impact trajectory. Moreover, if it is the case, we have to be sure that it won't be put on the trajectory of other keyholes. To this aim, we need a good knowledge of the 2029 region uncertainty and we will analyse the impact of the new observations of March 2011.
Published: 2011

42. Statistical analysis on the uncertainty of asteroid ephemerides

Author: Desmars, Josselin, Bancelin, David, Hestroffer, Daniel, Thuillot, William, Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Eds.: G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)
Subjects: Databases, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Physics::Space Physics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics::Earth and Planetary Astrophysics, Ephemerides, Asteroids, Dynamics
Abstract: International audience; The large number of asteroids allows a statistical analysis especially for their orbital uncertainty. It presents a particular interest for Near-Earth asteroids in order to estimate their close approach from Earth and eventually their risk of collision. Using ASTORB and MPCORB databases, we analyse the different uncertainty parameters (CEU, U) and highlight relations between the uncertainty parameter and the characteristics of the asteroid (orbital arc, absolute magnitude, ...).
Published: 2011

43. The equilibrium tide in viscoelastic parts of planets

Author: Remus, Françoise, Mathis, Stéphane, Zahn, Jean-Paul, Lainey, Valéry, Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Étude des Systèmes Informatiques et Automatiques (LESIA-INSA), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT), Eds.: G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)
Subjects: [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics::Earth and Planetary Astrophysics, planetary systems, dynamical evolution and stability, Physics::Geophysics
Abstract: International audience; Earth-like planets have viscoelastic mantles, whereas giant planets may have viscoelastic cores. As for the fluid parts of a body, the tidal dissipation of such solid regions, gravitationally perturbed by a companion body, highly depends on the tidal frequency, as well as on the rheology. Therefore, modelling tidal interactions presents a high interest to provide constraints on planet properties, and to understand their history and their evolution. Here, we examine the equilibrium tide in the solid core of a planet, taking into account the presence of a fluid envelope. We explain how to obtain the different Love numbers that describe its deformation. Next, we discuss how the quality factor Q depends on the chosen viscoelastic model. Finally, we show how the results may be implemented to describe the dynamical evolution of planetary systems.
Published: 2011

44. GETEMME: a mission to explore the martian satellites

Author: Le Poncin-Lafitte, Christophe, Lainey, Valéry, Core Team, The Getemme, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), The GETEMME core team, Eds.: G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)
Subjects: relativity, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], planetology, Physics::Space Physics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mars, Astrophysics::Earth and Planetary Astrophysics, space mission
Abstract: International audience; GETEMME (Gravity, Einstein's Theory, and Exploration of the Martian Moons' Environment) is a proposition of mission towards martian's moons. The spacecraft will initially rendezvous with Phobos and Deimos in order to carry out a comprehensive mapping and characterization of the two satellites and to deploy passive laser retro-reflectors on their surfaces. In the second stage of the mission, the spacecraft will be transferred into a lower 1500-km Mars orbit, to carry out routine laser range measurements to the Phobos and Deimos reflectors. Also, asynchronous two-way laser ranging measurements between the spacecraft and stations of the ILRS (International Laser Ranging Service) on Earth are foreseen. An onboard accelerometer will ensure a high accuracy for the spacecraft orbit determination. The inversion of all range and accelerometer data will allow us to determine or improve dramatically on a host of dynamic parameters of the Martian satellites system. From the complex motion and rotation of Phobos and Deimos we will obtain clues on internal structures and the origins of the satellites. Also, crucial data on the time-varying gravity field of Mars related to climate variation and internal structure will be obtained. Ranging measurements will also be essential to improve on several parameters in fundamental physics, such as the Post-Newtonian parameter β as well as time-rate changes of the gravitational constant and the Lense-Thirring effect. Measurements by GETEMME will firmly embed Mars and its satellites into the Solar System reference frame.
Published: 2011

45. Testing gravitation in the Solar System with radio science experiments

Author: Hees, A., Wolf, Peter, Lamine, Brahim, Reynaud, Serge, Jaekel, Marc Thierry, Le Poncin-Lafitte, Christophe, Lainey, Valéry, Dehant, Véronique, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Royal Observatory of Belgium [Brussels] (ROB), Laboratoire Kastler Brossel (LKB (Jussieu)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Théorique de l'ENS (LPTENS), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Eds.: G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Théorique de l'ENS [École Normale Supérieure] (LPTENS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics - Space Physics, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], radio science, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), General Relativity and Quantum Cosmology, Space Physics (physics.space-ph), tests of general relativity
Abstract: The laws of gravitation have been tested for a long time with steadily improving precision, leading at some moment of time to paradigmatic evolutions. Pursuing this continual effort is of great importance for science. In this communication, we focus on Solar System tests of gravity and more precisely on possible tests that can be performed with radio science observations (Range and Doppler). After briefly reviewing the current tests of gravitation at Solar System scales, we give motivations to continue such experiments. In order to obtain signature and estimate the amplitude of anomalous signals that could show up in radio science observables because of modified gravitational laws, we developed a new software that simulates Range/Doppler signals. We present this new tool that simulates radio science observables directly from the space-time metric. We apply this tool to the Cassini mission during its cruise from Jupiter to Saturn and derive constraints on the parameters entering alternative theories of gravity beyond the standard Parametrized Post Newtonian theory., Comment: proceedings of SF2A 2011 - minor changes (typos corrected - references updated)
Published: 2011

46. Some recent results of the CODALEMA experiment

Author: Rebai, Ahmed-Riadh, Laboratoire SUBATECH Nantes (SUBATECH), Mines Nantes (Mines Nantes)-Université de Nantes (UN)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud (eds), and CODALEMA
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), High Energy Physics - Experiment (hep-ex), Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], Astrophysics::Cosmology and Extragalactic Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract: National audience; Codalema is one of the experiments devoted to the detection of ultra high energy cosmic rays by the radio method. The main objective is to study the features of the radio signal induced by the development in the atmosphere of extensive air showers (EAS) generated by cosmic rays in the energy range of 10 PeV-1 EeV . After a brief presentation of the detector features, the main results obtained are reported (emission mechanism, lateral distribution of the electric field, energy calibration, etc.). The first studies of the radio wave front curvature are discussed as new preliminary results.
Published: 2011

47. The star formation rate density and dust attenuation evolution over 12 Gyr with the VVDS surveys

Author: Cucciati, O., Tresse, L., Ilbert, O., Le Fèvre, O., G. Alecian, K. Belkacem, R. Samadi and D. Valls-Gabaud, O. Cucciati, L. Tresse, O. Ilbert, O. . Fevre, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), and Tresse, Laurence
Subjects: cosmology: observation, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], cosmology: observations, luminosity function, [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph], galaxies: evolution, star formation, high-redshift
Abstract: International audience; We investigate the cosmic star formation rate density (SFRD) over ∼12 Gyr (0.05≤ z≤ 4.5), combining the VVDS Deep (17.5 ≤ I_{AB}≤ 24.0) and Ultra-Deep (23.00 ≤ i'_{AB} ≤ 24.75) surveys. We obtain a single homogeneous spectroscopic redshift sample, totalizing about 11000 galaxies. We estimate the rest-frame FUV luminosity function (LF) and luminosity density (LD), extract the dust attenuation of the FUV radiation using SED fitting, and derive the dust-corrected SFRD. We find a constant and flat faint-end slope alpha in the FUV LF at z2 it is on average brighter than in the literature, while φ^{*} is smaller. Our total LD shows a robust peak at z≃2, and the SFRD history peaks as well at z≃2. This peak is produced by the decreasing contribution at z2 the SFRD is entirely shaped by the high specific SFR galaxies. The presence of a fast rise at z>2 and of a clear peak at z≃2 of the SFRD is compelling for models of galaxy formation. The mean dust attenuation A_{FUV} of the global galaxy population rises by 1 mag from z=4.5 to z=2, reaches its maximum at z=1 (A_{FUV}≃2.2 mag), and then decreases by 1.1 mag down to z=0. The dust attenuation maximum is reached 2 Gyr after the SFRD peak, implying a contribution from the intermediate-mass stars to the dust production at z
Published: 2011

48. The Milky Way stellar populations in CFHTLS fields

Author: Guittet, Mélanie, Haywood, Misha, Schultheis, Mathias, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), G. Alecian, K. Belkacem, R. Samadi, D. Valls-Gabaud, and eds.
Subjects: Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Astrophysics of Galaxies, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics
Abstract: We 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 W1 and W3 fields, and compared with simulated maps produced using the Besan\c{c}on model. It is shown that the thick disk, represented in star-count models by a distinct component, is not an adequate description of the observed ([Fe/H], Z) distributions in these fields., Comment: 4 pages, 4 figures
Published: 2011
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49. In vivo determination of the anti-inflammatory and antioxidant effects of the aqueous extract of Syzygium aromaticum (clove) in an asthmatic rat model.

Author: Ounaceur LS, Messarah M, Lankar A, Touaibia D, Ghadab H, Garri Z, Boudjil S, Belkacem Djeffel K, Atoui L, Ounaceur A, Djaber N, and Boumendjel A
Subjects: Animals, Male, Ovalbumin, Catalase metabolism, Rats, Erythrocytes drug effects, Erythrocytes metabolism, Water chemistry, Antioxidants pharmacology, Plant Extracts pharmacology, Plant Extracts therapeutic use, Anti-Inflammatory Agents pharmacology, Anti-Inflammatory Agents therapeutic use, Syzygium chemistry, Asthma drug therapy, Asthma chemically induced, Asthma metabolism, Asthma pathology, Rats, Wistar, Disease Models, Animal, Bronchoalveolar Lavage Fluid chemistry, Lung drug effects, Lung pathology, Lung metabolism, Glutathione Peroxidase metabolism, Glutathione metabolism, Interleukin-4 metabolism, Interleukin-4 blood, Malondialdehyde metabolism
Abstract: Asthma is a chronic inflammatory disease of the airways strongly associated with interleukin-4 (IL-4), a cytokine that mediates and regulates various immune responses, including allergic reactions. This study aimed to evaluate the anti-inflammatory and antioxidant effects of an Aqueous Extract of Clove (AEC) Syzygium aromaticum on the lungs and erythrocytes of an experimental asthma model in Wistar rats. For this purpose, four groups of male rats were examined: control, sensitized with ovalbumin (OVA), treated with AEC, and treated with a combination of OVA/AEC. After treatment, the antioxidant effect was determined by measuring the malondialdehyde (MDA), glutathione peroxidase (GPx), glutathione (GSH), and catalase (CAT) levels. The anti-inflammatory effect was determined by measuring IL-4 levels by performing enzyme-linked immunosorbent assay (ELISA) using serum, lung, and bronchoalveolar lavage fluid (BALF) samples. A significant reduction (p ≤ 0.05) in the MDA levels and a significant increase (p ≤ 0.05) in the levels of GPx and CAT were observed in the lungs of rats treated with cloves. However, no statistically significant variation was observed in GSH levels. In erythrocytes, no statistically significant differences were observed between the experimental batches. Regarding the anti-inflammatory effect, the administration of S. aromaticum extract to sensitized rats resulted in a recovery in the levels of total proteins and IL-4 and a decrease in the three compartments studied (lungs, serum, and bronchoalveolar liquid). These results were confirmed by microscopic examination of lung histological sections. Overall, these findings confirmed that the AEC has anti-inflammatory and antioxidant effects.
Published: 2024
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50. Automatic detection of follicular regions in H&E images using iterative shape index.

Author: Belkacem-Boussaid K, Samsi S, Lozanski G, and Gurcan MN
Subjects: Algorithms, Diagnostic Imaging, Humans, Neoplasm Grading methods, Image Interpretation, Computer-Assisted, Lymphoma, Follicular pathology, Pattern Recognition, Automated methods
Abstract: Follicular Lymphoma (FL) accounts for 20-25% of non-Hodgkin lymphomas in the United States. The first step in grading FL is identifying follicles. Our paper discusses a novel technique to segment follicular regions in H&E stained images. The method is based on three successive steps: (1) region-based segmentation, (2) iterative shape index (concavity index) calculation, (3) and recursive watershed. A novel aspect of this method is the use of iterative Concavity Index (CI) to control the follicular splitting process in recursive watershed. CI takes into consideration the convex hull of the object and the closest area surrounding it. The mean Zijbendos similarity index (ZSI) final segmentation score on fifteen cases was 78.33%, with a standard deviation of 2.83., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
Published: 2011
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