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9 results on '"Lebreton, Y"'

1. About solar model calibration.

Author

Araki, H., Brézin, E., Ehlers, J., Frisch, U., Hepp, K., Jaffe, R. L., Kippenhahn, R., Weidenmüller, H. A., Wess, J., Zittartz, J., Beiglböck, W., Roxburgh, Ian W., Masnou, Jean-Louis, Morel, P., Berthomieu, G., Provost, J., and Lebreton, Y.

Abstract

A new value of the ratio of the heavy elements content to hydrogen abundance Z/X has been recently estimated in the solar atmosphere. We present the consequences of this result on the solar standard model and we examine the sensitivity to Z/X of the solar neutrinos flux predictions and of the oscillation frequencies. [ABSTRACT FROM AUTHOR]

Published
1995
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2. The CoRoT evolution and seismic tools activity.

Author

Lebreton, Y., Monteiro, M., Montalbán, J., Moya, A., Baglin, A., Christensen-Dalsgaard, J., Goupil, M.-J., Michel, E., Provost, J., Roxburgh, I., and Scuflaire, R.

Subjects
*SPACE sciences, *ASTEROSEISMOLOGY, *SEISMOLOGY, *EVOLUTIONARY theories, *NUMERICAL analysis
Abstract

The forthcoming data expected from space missions such as CoRoT require the capacity of the available tools to provide accurate models whose numerical precision is well above the expected observational errors. In order to secure that these tools meet the specifications, a team has been established to test and, when necessary, to improve the codes available in the community. The CoRoT Evolution and Seismic Tool Activity (ESTA) has been set up with this mission. Several groups have been involved. The present paper describes the motivation and the organisation of this activity, providing the context and the basis for the presentation of the results that have been achieved so far. This is not a finished task as future even better data will continue to demand more precise and complete tools for asteroseismology. [ABSTRACT FROM AUTHOR]

Published
2008
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3. CESAM: a free code for stellar evolution calculations.

Author

Morel, P. and Lebreton, Y.

Subjects
*STELLAR oscillations, *STELLAR evolution, *EVOLUTIONARY theories, *HYDROSTATICS, *POLYNOMIALS
Abstract

The cesam code is a consistent set of programs and routines which perform calculations of 1D quasi-hydrostatic stellar evolution including microscopic diffusion of chemical species and diffusion of angular momentum. The solution of the quasi-static equilibrium is performed by a collocation method based on piecewise polynomials approximations projected on a B-spline basis; that allows stable and robust calculations, and the exact restitution of the solution, not only at grid points, even for the discontinuous variables. Other advantages are the monitoring by only one parameter of the accuracy and its improvement by super-convergence. An automatic mesh refinement has been designed for adjusting the localisations of grid points according to the changes of unknowns. For standard models, the evolution of the chemical composition is solved by stiffly stable schemes of orders up to four; in the convection zones mixing and evolution of chemical are simultaneous. The solution of the diffusion equation employs the Galerkin finite elements scheme; the mixing of chemicals is then performed by a strong turbulent diffusion. A precise restoration of the atmosphere is allowed for. [ABSTRACT FROM AUTHOR]

Published
2008
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4. Inter-comparison of the g-, f- and p-modes calculated using different oscillation codes for a given stellar model.

Author

Moya, A., Christensen-Dalsgaard, J., Charpinet, S., Lebreton, Y., Miglio, A., Montalbán, J., Monteiro, M., Provost, J., Roxburgh, I., Scuflaire, R., Suárez, J., and Suran, M.

Subjects
STELLAR oscillations, ASTEROSEISMOLOGY, SEISMOLOGY, NUMERICAL analysis, EQUILIBRIUM
Abstract

In order to make asteroseismology a powerful tool to explore stellar interiors, different numerical codes should give the same oscillation frequencies for the same input physics. Any differences found when comparing the numerical values of the eigenfrequencies will be an important piece of information regarding the numerical structure of the code. The ESTA group was created to analyze the non-physical sources of these differences. The work presented in this report is a part of Task 2 of the ESTA group. Basically the work is devoted to test, compare and, if needed, optimize the seismic codes used to calculate the eigenfrequencies to be finally compared with observations. The first step in this comparison is presented here. The oscillation codes of nine research groups in the field have been used in this study. The same physics has been imposed for all the codes in order to isolate the non-physical dependence of any possible difference. Two equilibrium models with different grids, 2172 and 4042 mesh points, have been used, and the latter model includes an explicit modelling of semiconvection just outside the convective core. Comparing the results for these two models illustrates the effect of the number of mesh points and their distribution in particularly critical parts of the model, such as the steep composition gradient outside the convective core. A comprehensive study of the frequency differences found for the different codes is given as well. These differences are mainly due to the use of different numerical integration schemes. The number of mesh points and their distribution are crucial for interpreting the results. The use of a second-order integration scheme plus a Richardson extrapolation provides similar results to a fourth-order integration scheme. The proper numerical description of the Brunt-Väisälä frequency in the equilibrium model is also critical for some modes. This influence depends on the set of the eigenfunctions used for the solution of the differential equations. An unexpected result of this study is the high sensitivity of the frequency differences to the inconsistent use of values of the gravitational constant ( G) in the oscillation codes, within the range of the experimentally determined ones, which differ from the value used to compute the equilibrium model. This effect can provide differences for a given equilibrium model substantially larger than those resulting from the use of different codes or numerical techniques; the actual differences between the values of G used by the different codes account for much of the frequency differences found here. [ABSTRACT FROM AUTHOR]

Published
2008
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5. SEISMIC DIAGNOSTICS OF STELLAR CONVECTION TREATMENT FROM OSCILLATION AMPLITUDES OF P-MODES.

Author

Samadi, R., Goupil, M. J., Lebreton, Y., Nordlund, Å., and Baudin, F.

Subjects
SUN, SOLAR oscillations, CONVECTION (Astrophysics), ANISOTROPY, STELLAR mass, TURBULENCE
Abstract

The excitation rate P of solar p-modes is computed with a model of stochastic excitation which involves constraints on the averaged properties of the solar turbulence. These constraints are obtained from a 3D simulation. Resulting values for P are found ∼ 4.5 times larger than when the calculation assumes properties of turbulent convection which are derived from an 1D solar model based on Gough (1977)'s formulation of the mixing-length theory (GMLT). This difference is mainly due to the assumed values for the mean anisotropy of the velocity field in each case. Calculations based on 3D constraints bring the P maximum closer to the observational one. We also compute P for several models of intermediate mass stars (1 ≲ M ≲ 2 M[This symbol cannot be presented in ASCII format]). Differences in the values of Pmax between models computed with the classical mixing-length theory and GMLT models are found large enough for main sequence stars to suggest that measurements of P in this mass range will be able to discriminate between different models of turbulent convection. [ABSTRACT FROM AUTHOR]

Published
2003
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6. Old, Low-Mass, Metal-Rich (SMR) Stars.

Author

Cayrel de Strobel, G., Lebreton, Y., Soubiran, C., and Friel, E.D.

Abstract

The authors of this paper try to disentangle the many problems arisen from a new enlarged sample of nearby low-mass,metal-rich-stars. These stars have reliable absolute magnitudes, deduced from Hipparcos parallaxes, precise bolometric corrections, effective temperatures and metal abundances from high resolution detailed spectroscopic analyses. Their ages have been derived from a grid of isochrones calculated with up to date physics. The main goal of this paper is to determine the ages of the slightly evolved SMR stars. Among those with well determinated ages about 80% of them have intermediate ages of (2 to 5 Gyr), but only 20% have ages of 8 Gyr or more. Nevertheless, the existence of very old metal-rich stars is confirmed. [ABSTRACT FROM AUTHOR]

Published
1999
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7. Survival of 6Li, and 7Li, in Metal-Poor Stars.

Author

Cayrel, R., Lebreton, Y., and Morel, P.

Abstract

The relationship between the depletions of 6Li and 7Li is studied for two models of lithium burning, below the convective zone. The parametersof the depletion models are submitted to the constraint that the slope ofthe 7Li theoretical depletion curve agrees with the slope of theobserved depletion curve, for cool subdwarfs. Other less restrictive modelsare also considered.In all cases, a 6Li depletion less than 0.5 dex implies a 7Lidepletion less than 0.1 dex. With the constraint on the slope of the7Li curve, the depletion of 7Li for the same depletion of 6Li is below 0.05 dex. The still unsolved problem for the true 7Li abundance in subdwarfs is the possible influence of temperature inhomogeneities, raised by Kurucz,subsequently shown to be small in the solar case, but not yet computed withthe inclusion of departure from LTE for metal-poor stars. [ABSTRACT FROM AUTHOR]

Published
1999
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9. Age dating of an early Milky Way merger via asteroseismology of the naked-eye star ν Indi

Author

William J. Chaplin, Aldo M. Serenelli, Andrea Miglio, Thierry Morel, J. Ted Mackereth, Fiorenzo Vincenzo, Hans Kjeldsen, Sarbani Basu, Warrick H. Ball, Amalie Stokholm, Kuldeep Verma, Jakob Rørsted Mosumgaard, Victor Silva Aguirre, Anwesh Mazumdar, Pritesh Ranadive, H. M. Antia, Yveline Lebreton, Joel Ong, Thierry Appourchaux, Timothy R. Bedding, Jørgen Christensen-Dalsgaard, Orlagh Creevey, Rafael A. García, Rasmus Handberg, Daniel Huber, Steven D. Kawaler, Mikkel N. Lund, Travis S. Metcalfe, Keivan G. Stassun, Michäel Bazot, Paul G. Beck, Keaton J. Bell, Maria Bergemann, Derek L. Buzasi, Othman Benomar, Diego Bossini, Lisa Bugnet, Tiago L. Campante, Zeynep Çelik Orhan, Enrico Corsaro, Lucía González-Cuesta, Guy R. Davies, Maria Pia Di Mauro, Ricky Egeland, Yvonne P. Elsworth, Patrick Gaulme, Hamed Ghasemi, Zhao Guo, Oliver J. Hall, Amir Hasanzadeh, Saskia Hekker, Rachel Howe, Jon M. Jenkins, Antonio Jiménez, René Kiefer, James S. Kuszlewicz, Thomas Kallinger, David W. Latham, Mia S. Lundkvist, Savita Mathur, Josefina Montalbán, Benoit Mosser, Andres Moya Bedón, Martin Bo Nielsen, Sibel Örtel, Ben M. Rendle, George R. Ricker, Thaíse S. Rodrigues, Ian W. Roxburgh, Hossein Safari, Mathew Schofield, Sara Seager, Barry Smalley, Dennis Stello, Róbert Szabó, Jamie Tayar, Nathalie Themeßl, Alexandra E. L. Thomas, Roland K. Vanderspek, Walter E. van Rossem, Mathieu Vrard, Achim Weiss, Timothy R. White, Joshua N. Winn, Mutlu Yıldız, European Commission, European Research Council, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Generalitat de Catalunya, Chaplin W.J., Serenelli A.M., Miglio A., Morel T., Mackereth J.T., Vincenzo F., Kjeldsen H., Basu S., Ball W.H., Stokholm A., Verma K., Mosumgaard J.R., Silva Aguirre V., Mazumdar A., Ranadive P., Antia H.M., Lebreton Y., Ong J., Appourchaux T., Bedding T.R., Christensen-Dalsgaard J., Creevey O., Garcia R.A., Handberg R., Huber D., Kawaler S.D., Lund M.N., Metcalfe T.S., Stassun K.G., Bazot M., Beck P.G., Bell K.J., Bergemann M., Buzasi D.L., Benomar O., Bossini D., Bugnet L., Campante T.L., Orhan Z.C., Corsaro E., Gonzalez-Cuesta L., Davies G.R., Di Mauro M.P., Egeland R., Elsworth Y.P., Gaulme P., Ghasemi H., Guo Z., Hall O.J., Hasanzadeh A., Hekker S., Howe R., Jenkins J.M., Jimenez A., Kiefer R., Kuszlewicz J.S., Kallinger T., Latham D.W., Lundkvist M.S., Mathur S., Montalban J., Mosser B., Bedon A.M., Nielsen M.B., Ortel S., Rendle B.M., Ricker G.R., Rodrigues T.S., Roxburgh I.W., Safari H., Schofield M., Seager S., Smalley B., Stello D., Szabo R., Tayar J., Themessl N., Thomas A.E.L., Vanderspek R.K., van Rossem W.E., Vrard M., Weiss A., White T.R., Winn J.N., Yildiz M., Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Department of Psychology, St John's University, Institute of Space Sciences [Barcelona] (ICE-CSIC), Spanish National Research Council [Madrid] (CSIC), School of Physics and Astronomy, University of Birmingham [Birmingham], Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Danish AsteroSeismology Centre (DASC), Aarhus University [Aarhus], Department of Astronomy, Yale University [New Haven], Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, Institut de Physique de Rennes (IPR), Université de Rennes (UR)-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), 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), 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), Sydney Institute for Astronomy (SIfA), The University of Sydney, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 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, 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), Research institute of Computer Vision and Robotics [Girona] (VICOROB), Universitat de Girona (UdG), Department of Physics and Astronomy [Aarhus], Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], 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), Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Istituto Nazionale di Astrofisica (INAF), 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), NASA Ames Research Center (ARC), Centre for Automation and Robotics (CAR), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad Politécnica de Madrid (UPM), Kiepenheuer-Institut für Sonnenphysik (KIS), Stellar Astrophysics Centre [Aarhus] (SAC), Instituut voor Sterrenkunde [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), High Altitude Observatory (HAO), National Center for Atmospheric Research [Boulder] (NCAR), Département des Sciences et Gestion de l'Environnement/Océanologie [Liège], Université de Liège, Center for Space Research [Cambridge] (CSR), Massachusetts Institute of Technology (MIT), High Speed Networks Laboratory, Dept. of Telecommunications and Media Informatics, Budapest University of Technology and Economics [Budapest] (BME), Department of Astronomy (Ohio State University), Ohio State University [Columbus] (OSU), Observatoire de Paris, Université Paris sciences et lettres (PSL), Ege Üniversitesi, CERFACS [Toulouse], 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)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-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, 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), Universidad Politécnica de Madrid (UPM)-Consejo Superior de Investigaciones Científicas [Spain] (CSIC), PSL Research University (PSL), 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), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, Milky Way, Population, GAIA, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, MASS, CHEMICAL-COMPOSITION, Q1, 01 natural sciences, Asteroseismology, 0103 physical sciences, QB460, Satellite galaxy, STELLAR HALOES, Astrophysics::Solar and Stellar Astrophysics, 10. No inequality, education, 010303 astronomy & astrophysics, QB600, QC, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Dwarf galaxy, QB, Physics, [PHYS]Physics [physics], education.field_of_study, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], ACCRETION HISTORY, Astronomy and Astrophysics, DISC, Astrophysics - Astrophysics of Galaxies, Galaxy, MODEL, Stars, Astrophysics - Solar and Stellar Astrophysics, DARK-MATTER HALOES, ROTATION, Halo, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], SOLAR-LIKE OSCILLATIONS, QB799
Abstract

This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). et al., Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies. Although these accreted stellar populations can be forensically identified as kinematically distinct structures within the Galaxy, it is difficult in general to date precisely the age at which any one merger occurred. Recent results have revealed a population of stars that were accreted via the collision of a dwarf galaxy, called Gaia–Enceladus, leading to substantial pollution of the chemical and dynamical properties of the Milky Way. Here we identify the very bright, naked-eye star ν Indi as an indicator of the age of the early in situ population of the Galaxy. We combine asteroseismic, spectroscopic, astrometric and kinematic observations to show that this metal-poor, alpha-element-rich star was an indigenous member of the halo, and we measure its age to be 11.0±0.7 (stat) ±0.8 (sys) billion years. The star bears hallmarks consistent with having been kinematically heated by the Gaia–Enceladus collision. Its age implies that the earliest the merger could have begun was 11.6 and 13.2 billion years ago, at 68% and 95% confidence, respectively. Computations based on hierarchical cosmological models slightly reduce the above limits., J.M. acknowledge support from the ERC Consolidator Grant funding scheme (project ASTEROCHRONOMETRY, grant agreement number 772293). A.M.S. is partially supported by the Spanish Government (ESP2017-82674-R) and Generalitat de Catalunya (2017-SGR-1131). T.L.C. acknowledges support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement number 792848 (PULSATION). K.J.B., S.H., J.S.K. and N.T. are supported by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement number 338251 (StellarAges). E.C. is funded by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement number 664931. L.G.-C. acknowledges support from the MINECO FPI-SO doctoral research project SEV-2015-0548-17-2 and predoctoral contract BES-2017-082610. S.M. acknowledges support from the Spanish ministry through the Ramon y Cajal fellowship number RYC-2015-17697. This work was supported by FEDER through COMPETE2020 (POCI-01-0145-FEDER-030389. A.M.B. acknowledges funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 749962 (project THOT).

Published
2020

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