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1. Velocity-intensity asymmetry reversal of solar radial p-modes

Author: Reza Samadi, C. Barban, J. Philidet, Hans-Günter Ludwig, Kevin Belkacem, 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Zentrum für Astronomie der Universität Heidelberg (ZAH), and Universität Heidelberg [Heidelberg]
Subjects: 010504 meteorology & atmospheric sciences, media_common.quotation_subject, FOS: Physical sciences, Astrophysics, 01 natural sciences, Asymmetry, Spectral line, methods: analytical, Radiative flux, Quality (physics), 0103 physical sciences, stars: atmospheres, Sun: oscillations, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Line (formation), media_common, Sun: helioseismology, Physics, Spectral density, Astronomy and Astrophysics, stars: solar-type, Intensity (physics), Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, [SDU]Sciences of the Universe [physics], stars: oscillations, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The development of space-borne missions has significantly improved the quality of the measured spectra of solar-like oscillators. Their $p$-mode line profiles can now be resolved, and the asymmetries inferred for a variety of stars other than the Sun. However, it has been known for a long time that the asymmetries of solar $p$-modes are reversed between the velocity and the intensity spectra. Understanding the origin of this reversal is necessary in order to use asymmetries as a tool for seismic diagnosis. For stars other than the Sun, only the intensity power spectrum is sufficiently resolved to allow for an estimation of mode asymmetries. We recently developed an approach designed to model and predict these asymmetries in the velocity power spectrum of the Sun and to successfully compare them to their observationally derived counterparts. In this paper we expand our model and predict the asymmetries featured in the intensity power spectrum. We find that the shape of the mode line profiles in intensity is largely dependent on how the oscillation-induced variations of the radiative flux are treated, and that modelling it realistically is crucial to understanding asymmetry reversal. Perturbing a solar-calibrated grey atmosphere model, and adopting the quasi-adiabatic framework as a first step, we reproduce the asymmetries observed in the solar intensity spectrum for low-frequency modes. We conclude that, unlike previously thought, it is not necessary to invoke an additional mechanism (e.g. non-adiabatic effects, coherent non-resonant background signal) to explain asymmetry reversal. This additional mechanism is necessary, however, to explain asymmetry reversal for higher-order modes., Comment: 9 pages, 4 figures. Accepted for publication in A&A
Published: 2020
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2. Calibration of mixing-length parameter α for MLT and FST models by matching with CO 5 BOLD models

Author: Josefina Montalbán, T. Sonoi, Reza Samadi, M. J. Goupil, Hans-Günter Ludwig, Marc-Antoine Dupret, Kevin Belkacem, E. Caffau, 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), Zentrum für Astronomie der Universität Heidelberg (ZAH), Universität Heidelberg [Heidelberg], Galaxies, Etoiles, Physique, Instrumentation (GEPI), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), 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), and PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Photosphere, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Red giant, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Metallicity, Astronomy and Astrophysics, Context (language use), Astrophysics, Effective temperature, Surface gravity, 01 natural sciences, Computational physics, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Stellar evolution, Free parameter
Abstract: Context.Space observations by the CoRoT andKeplermissions have provided a wealth of high-quality seismic data for a large number of stars from the main sequence to the red giant phases. One main goal of these missions is to take advantage of the rich spectra of solar-like oscillations to perform precise determinations of stellar characteristic parameters. To make the best of such data, we need theoretical stellar models with a precise near-surface structure since a near-surface structure of a solar-like star has significant influence on solar-like oscillation frequencies. The mixing-length parameter is a key factor to determine the near-surface structure of stellar models. In current versions of the convection formulations used in stellar evolution codes, the mixing-length parameter is a free parameter that needs to be properly specified.Aims.We aim at determining appropriate values of the mixing-length parameter,α, to be used consistently with the adopted convection formulation when computing stellar evolution models across the Hertzsprung–Russell diagram. This determination is based on 3D hydrodynamical simulation models.Methods.We calibratedαvalues by matching entropy profiles of 1D envelope models with those of hydrodynamical 3D models of solar-like stars produced by the CO5BOLD code. For such calibration, previous works concentrated on the classical mixing-length theory (MLT). We also analyzed full spectrum turbulence (FST) models. To construct the atmosphere in the 1D models, we used the Eddington grayT(τ) relation and that with the solar-calibrated Hopf-like function.Results.For both MLT and FST models with a mixing lengthl = αHp, calibratedαvalues increase with increasing surface gravity or decreasing effective temperature. For the FST models, we carried out an additional calibration using anα*value defined asl = rtop − r + α*Hp, top, whereα*is found to increase with surface gravity and effective temperature. We provide tables of the calibratedαvalues across theTeff–log g plane for solar metallicity. By computing stellar evolution with varyingαbased on our 3Dαcalibration, we find that the change from solarαto varyingαshifts evolutionary tracks particularly for the FST model. As for the correspondence to the 3D models, the solar Hopf-like function generally gives a photospheric-minimum entropy closer to a 3D model than the EddingtonT(τ). The structure below the photosphere depends on the adopted convection model. However, we cannot obtain a definitive conclusion about which convection model gives the best correspondence to the 3D models. This is because each 1D physical quantity is related via an equation of state (EoS), but it is not the case for the averaged 3D quantities. Although the FST models withl = rtop − r + α*Hp, topare found to give the oscillation frequencies closest to the solar observed frequencies, their acoustic cavities are formed with compensatory effects between deviating density and temperature profiles near the top of the convective envelope. In future work, an appropriate treatment of the top part of the 1D convective envelope is necessary, for example, by considering turbulent pressure and overshooting.
Published: 2019
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3. Influence of metallicity on the near-surface effect on oscillation frequencies

Author: L. Manchon, Hans-Günter Ludwig, T. Sonoi, Elisabetta Caffau, Reza Samadi, J. P. Marques, Kevin Belkacem, 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), Astronomical Institute [Sendai], Tohoku University [Sendai], Galaxies, Etoiles, Physique, Instrumentation (GEPI), 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], PSL Research University (PSL)-PSL Research University (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)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], 010504 meteorology & atmospheric sciences, Opacity, Metallicity, Context (language use), Astrophysics, asteroseismology, 01 natural sciences, Asteroseismology, law.invention, law, stars: low-mass, 0103 physical sciences, 010303 astronomy & astrophysics, Stellar evolution, Scaling, convection, 0105 earth and related environmental sciences, Physics, Astronomy and Astrophysics, stars: solar-type, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, stars: oscillations, Hydrostatic equilibrium
Abstract: The CoRoT and Kepler missions have provided high-quality measurements of the frequency spectra of solar-like pulsators, enabling us to probe stellar interiors with a very high degree of accuracy by comparing the observed and modeled frequencies. However, the frequencies computed with 1D models suffer from systematic errors related to the poor modeling of the uppermost layers of stars. These biases are what is commonly named the near surface effect. The dominant effect is related to the turbulent pressure that modifies the hydrostatic equilibrium and thus the frequencies. This has already been investigated using grids of 3D RMHD simulations, which also were used to constrain the parameters of the empirical correction models. However, the effect of metallicity has not been considered so far. We study the impact of metallicity on the surface effect across the HR diagram, and provide a method for accounting for it when using the empirical correction models. We computed a grid of patched 1D stellar models with the stellar evolution code CESTAM in which poorly modeled surface layers have been replaced by averaged stratification computed with the 3D RMHD code CO5BOLD. We found that metallicity has a strong impact on the surface effect: keeping T_eff and log g constant, the frequency residuals can vary by up to a factor two. Therefore, the influence of metallicity cannot be neglected. We found that a correct way of accounting for it is to consider the surface Rosseland mean opacity. It allowed us to give a physically-grounded justification as well as a scaling relation for the frequency differences at nu_max as a function of T_eff, log g and kappa. Finally, we provide prescriptions for the fitting parameters of the correction functions. We show that the impact of metallicity through the Rosseland mean opacity must be taken into account when studying and correcting the surface effect., Comment: 15 pages, 7 figures. Accepted for publication in A&A
Published: 2018
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4. Dipole modes with depressed amplitudes in red giants are mixed modes

Author: Masao Takata, Reza Samadi, C. Pinçon, Kevin Belkacem, Thomas Kallinger, C. Barban, Mathieu Vrard, M. J. Goupil, Benoit Mosser, 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), Kavli Institute for Theoretical Physics [Santa Barbara] (KITP), University of California [Santa Barbara] (UC Santa Barbara), University of California (UC)-University of California (UC), Department of Physics and Astronomy [Vancouver], University of British Columbia (UBC), University of California [Santa Barbara] (UCSB), and University of California-University of California
Subjects: FOS: Physical sciences, Context (language use), Astrophysics, stars: interiors, 01 natural sciences, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, 010306 general physics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Oscillation, Mode (statistics), stars: magnetic field, Astronomy and Astrophysics, Magnetic field, Stars, Dipole, Amplitude, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, stars: oscillations, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Seismic observations have shown that a number of evolved stars exhibit low-amplitude dipole modes, which are referred to as depressed modes. Recently, these low amplitudes have been attributed to the presence of a strong magnetic field in the stellar core of those stars. We intend to study the properties of depressed modes in evolved stars, which is a necessary condition before concluding on the physical nature of the mechanism responsible for the reduction of the dipole mode amplitudes. We perform a thorough characterization of the global seismic parameters of depressed dipole modes and show that these modes have a mixed character. The observation of stars showing dipole mixed modes that are depressed is especially useful for deriving model-independent conclusions on the dipole mode damping. Observations prove that depressed dipole modes in red giants are not pure pressure modes but mixed modes. This result invalidates the hypothesis that the depressed dipole modes result from the suppression of the oscillation in the radiative core of the stars. Observations also show that, except for the visibility, the seismic properties of the stars with depressed modes are equivalent to those of normal stars. The mixed nature of the depressed modes in red giants and their unperturbed global seismic parameters carry strong constraints on the physical mechanism responsible for the damping of the oscillation in the core. This mechanism is able to damp the oscillation in the core but cannot fully suppress it. Moreover, it cannot modify the radiative cavity probed by the gravity component of the mixed modes. The recent mechanism involving high magnetic field proposed for explaining depressed modes is not compliant with the observations and cannot be used to infer the strength and the prevalence of high magnetic fields in red giants., accepted in A&A
Published: 2017
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5. Helium signature in red giant oscillation patterns observed by Kepler

Author: Saskia Hekker, C. Barban, Pierre Beck, Benoit Mosser, Reza Samadi, Mathieu Vrard, Thomas Kallinger, Kevin Belkacem, Y. P. Elsworth, 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 [Birmingham], University of Alabama at Birmingham [ Birmingham] (UAB), Stellar Astrophysics Centre [Aarhus] (SAC), Aarhus University [Aarhus], University of Vienna [Vienna], Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, 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), ANR-12-BS05-0008,IDEE,Influence Des Etoiles sur les Exoplanètes(2012), European Project: 338251,EC:FP7:ERC,ERC-2013-StG,STELLARAGES(2013), Max-Planck-Institut für Sonnensystemforschung (MPS), 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: solar-type [stars], oscillations [stars], Red giant, chemistry.chemical_element, FOS: Physical sciences, Context (language use), Astrophysics, stars: interiors, DEPENDENCE, Ionization, Modulation (music), Astrophysics::Solar and Stellar Astrophysics, stars: evolution, Helium, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, interiors [stars], Physics, Oscillation, SOLAR CONVECTIVE ENVELOPE, Mode (statistics), Astronomy and Astrophysics, stars: solar-type, Stars, Astrophysics - Solar and Stellar Astrophysics, chemistry, Space and Planetary Science, evolution [stars], MODES, IONIZATION, LARGE FREQUENCY SEPARATION, Astrophysics::Earth and Planetary Astrophysics, stars: oscillations, SPACINGS, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], STARS
Abstract: The space-borne missions CoRoT and Kepler have provided a large amount of precise photometric data. Among the stars observed, red giants show a rich oscillation pattern that allows their precise characterization. Long-duration observations allow for investigating the fine structure of this oscillation pattern. A common pattern of oscillation frequency was observed in red giant stars, which corresponds to the second-order development of the asymptotic theory. This pattern, called the universal red giant oscillation pattern, describes the frequencies of stellar acoustic modes. We aim to investigate the deviations observed from this universal pattern, thereby characterizing them in terms of the location of the second ionization zone of helium. We also show how this seismic signature depends on stellar evolution. We measured the frequencies of radial modes with a maximum likelihood estimator method, then we identified a modulation corresponding to the departure from the universal oscillation pattern. We identify the modulation component of the radial mode frequency spacings in more than five hundred red giants. The variation in the modulation that we observe at different evolutionary states brings new constraints on the interior models for these stars. We also derive an updated form of the universal pattern that accounts for the modulation and provides highly precise radial frequencies., Comment: 10 pages, 9 figures, accepted by A&A. AA/2014/25064
Published: 2015
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6. Solar-like oscillations in distant stars as seen by CoRoT : the special case of HD 42618, a solar sister

Author: Guy R. Davies, Frédéric Baudin, Savita Mathur, Ian W. Roxburgh, Reza Samadi, C. Régulo, Graham A. Verner, Patrick Boumier, Othman Benomar, Jérôme Ballot, Benoit Mosser, M. P. Hall, Kevin Belkacem, M. J. Goupil, Rafael A. García, Thierry Morel, C. Barban, Ennio Poretti, Sébastien Deheuvels, Eric Michel, Yveline Lebreton, 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), Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, 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), Insituto Geofísico, Escuela Politécnica Nacional (EPN), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Convection, Physics, History, 010504 meteorology & atmospheric sciences, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy, Astrophysics, Radius, Star (graph theory), Light curve, 01 natural sciences, Computer Science Applications, Education, Stars, Spitzer Space Telescope, 0103 physical sciences, Solar-like oscillations, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Envelope (waves)
Abstract: We report the observations of a main-sequence star, HD 42618 (Teff = 5765 K, G3V) by the space telescope CoRoT. This is the closest star to the Sun ever observed by CoRoT in term of its fundamental parameters. Using a preliminary version of CoRoT light curves of HD 42618, p modes are detected around 3.2 mHz associated to l = 0, 1 and 2 modes with a large spacing of 142 μHz. Various methods are then used to derive the mass and radius of this star (scaling relations from solar values as well as comparison between theoretical and observationnal frequencies) giving values in the range of (0.80 − 1.02)M⊙ and (0.91 − 1.01)R⊙. A preliminary analysis of l = 0 and 1 modes allows us also to study the amount of penetrative convection at the base of the convective envelope.
Published: 2013
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7. Seismic diagnostics for transport of angular momentum in stars II. Interpreting observed rotational splittings of slowly rotating red giant stars

Author: Reza Samadi, Marie-Jo Goupil, Benoit Mosser, Yveline Lebreton, Kevin Belkacem, R. M. Ouazzani, J. P. Marques, 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), 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), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Angular momentum, Red giant, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, stars: interiors, Rotation, 01 natural sciences, Asteroseismology, Frequency separation, stars: rotation, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Envelope (waves), Physics, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Stars, Space and Planetary Science, Excited state, Astrophysics::Earth and Planetary Astrophysics, stars: oscillations
Abstract: International audience; Asteroseismology with the space-borne missions CoRoT and Kepler provides a powerful mean of testing the modeling of transport processes in stars. Rotational splittings are currently measured for a large number of red giant stars and can provide stringent constraints on the rotation profiles. The aim of this paper is to obtain a theoretical framework for understanding the properties of the observed rotational splittings of red giant stars with slowly rotating cores. This allows us to establish appropriate seismic diagnostics for rotation of these evolved stars. Rotational splittings for stochastically excited dipolar modes are computed adopting a first-order perturbative approach for two $1.3 M_\odot$ benchmark models assuming slowly rotating cores. For red giant stars with slowly rotating cores, we show that the variation of the rotational splittings of $\ell=1$ modes with frequency depends only on the large frequency separation, the g-mode period spacing, and the ratio of the average envelope to core rotation rates (${\cal R}$). This leds us to propose a way to infer directly ${\cal R}$ from the observations. This method is validated using the Kepler red giant star KIC 5356201. Finally, we provide a theoretical support for the use of a Lorentzian profile to measure the observed splittings for red giant stars.
Published: 2013
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8. Spin down of the core rotation in red giants

Author: Savita Mathur, M. J. Goupil, Robert L. Morris, Rafael A. García, S. Deheuvels, C. Barban, Steven Bloemen, Jie Li, Marc H. Pinsonneault, Kevin Belkacem, J. P. Marques, Thomas Kallinger, Dennis Stello, Y. P. Elsworth, Todd C. Klaus, Rhita-Maria Ouazzani, J. De Ridder, Paul G. Beck, Saskia Hekker, Reza Samadi, Benoit Mosser, 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), Georg-August-University [Göttingen], Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen]-Radboud university [Nijmegen], 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 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), School of Physics and Astronomy, University of Birmingham [Birmingham], Institute for Astronomy [Vienna], University of Vienna [Vienna], Departments of Astronomy and Chemistry, The Ohio State University, Ohio State University [Columbus] (OSU), School of Physics [UNSW Sydney] (UNSW), University of New South Wales [Sydney] (UNSW), Institut d'Électronique et des Technologies du numéRique (IETR), Nantes Université (NU)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Space Science Institute [Boulder] (SSI), Department of Experimental Pathology, Guy's Hospital (UMDS), Low Energy Astrophysics (API, FNWI), Georg-August-University = Georg-August-Universität Göttingen, Radboud University [Nijmegen]-Radboud University [Nijmegen], 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), 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 de Nantes (UN)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), and Université de Nantes (UN)-Université de Rennes 1 (UR1)
Subjects: Stellar mass, Red giant, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Rotation, 01 natural sciences, Asteroseismology, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, oscillations, interiors, rotation, late-type, 010303 astronomy & astrophysics, Stellar evolution, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, [PHYS]Physics [physics], 010308 nuclear & particles physics, White dwarf, Astronomy and Astrophysics, Red-giant branch, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The space mission Kepler provides us with long and uninterrupted photometric time series of red giants. We are now able to probe the rotational behaviour in their deep interiors using the observations of mixed modes. We aim to measure the rotational splittings in red giants and to derive scaling relations for rotation related to seismic and fundamental stellar parameters. We have developed a dedicated method for automated measurements of the rotational splittings in a large number of red giants. Ensemble asteroseismology, namely the examination of a large number of red giants at different stages of their evolution, allows us to derive global information on stellar evolution. We have measured rotational splittings in a sample of about 300 red giants. We have also shown that these splittings are dominated by the core rotation. Under the assumption that a linear analysis can provide the rotational splitting, we observe a small increase of the core rotation of stars ascending the red giant branch. Alternatively, an important slow down is observed for red-clump stars compared to the red giant branch. We also show that, at fixed stellar radius, the specific angular momentum increases with increasing stellar mass. Ensemble asteroseismology indicates what has been indirectly suspected for a while: our interpretation of the observed rotational splittings leads to the conclusion that the mean core rotation significantly slows down during the red giant phase. The slow-down occurs in the last stages of the red giant branch. This spinning down explains, for instance, the long rotation periods measured in white dwarfs, Accepted in A&A
Published: 2012
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9. Mode lifetime and associated scaling relations

Author: Kevin Belkacem, J. P. Marques, M. A. Dupret, Thierry Appourchaux, Frédéric Baudin, M. J. Goupil, Reza Samadi, Arlette 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), 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, and Institut für Astrophysik, Universität Göttingen
Subjects: Physics, QC1-999, Mode (statistics), Spectral density, Effective temperature, 01 natural sciences, Kepler, Asteroseismology, Theoretical physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010306 general physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Scaling
Abstract: International audience; Thanks to the CoRoT and Kepler spacecrafts, scaling relations (linking seismic indices and global stellar parameters) are becoming the cornerstone of ensemble asteroseismology. Among them, the relation between the cut-off frequency and the frequency of the maximum in the power spectrum of solar-like pulsators as well as the relation between mode lifetime and the effective temperature remain poorly understood. However, a solid theoretical background is essential to assess the accuracy of those relations and subsequently of the derived stellar parameters. We will thus present recent advances on the understanding of the underlying mechanisms governing those relations and show that the physics of mode lifetime (thus of mode damping) plays a major role.
Published: 2012
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10. Modelling a high-mass red giant observed by CoRoT

Author: Hans Bruntt, Michel Auvergne, Thomas Kallinger, B. Mosser, J. De Ridder, Thierry Morel, Frédéric Baudin, Marie-Jo Goupil, Claude Catala, Eric Michel, Saskia Hekker, Annie Baglin, Artie P. Hatzes, Yveline Lebreton, Reza Samadi, Laure Lefèvre, Fabien Carrier, C. Barban, 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), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université de Liège, Contract PRODEX GAIA-DPAC, Netherlands Organisation for Scientific Research (NWO), FWO-Flanders under project O6260 - G.0728.11, Low Energy Astrophysics (API, FNWI), 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), and 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)
Subjects: Red giant, Metallicity, Star (game theory), stars: individual: HD 50890, FOS: Physical sciences, chemistry.chemical_element, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, asteroseismology, stars: interiors, stars: individual: HIP 33243, 01 natural sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Red clump, Solar and Stellar Astrophysics (astro-ph.SR), Helium, Astrophysics::Galaxy Astrophysics, Physics, stars: individual: HR 2582, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Order (ring theory), Astronomy and Astrophysics, Light curve, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Red-giant branch, Astrophysics - Solar and Stellar Astrophysics, chemistry, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, stars: oscillations, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The G6 giant HR\,2582 (HD\,50890) was observed by CoRoT for approximately 55 days. Mode frequencies are extracted from the observed Fourier spectrum of the light curve. Numerical stellar models are then computed to determine the characteristics of the star (mass, age, etc...) from the comparison with observational constraints. We provide evidence for the presence of solar-like oscillations at low frequency, between 10 and 20\,$\mu$Hz, with a regular spacing of $(1.7\pm0.1)\mu$Hz between consecutive radial orders. Only radial modes are clearly visible. From the models compatible with the observational constraints used here, We find that HR\,2582 (HD\,50890) is a massive star with a mass in the range (3--\,5\,$M_{\odot}$), clearly above the red clump. It oscillates with rather low radial order ($n$ = 5\,--\,12) modes. Its evolutionary stage cannot be determined with precision: the star could be on the ascending red giant branch (hydrogen shell burning) with an age of approximately 155 Myr or in a later phase (helium burning). In order to obtain a reasonable helium amount, the metallicity of the star must be quite subsolar. Our best models are obtained with a mixing length significantly smaller than that obtained for the Sun with the same physical description (except overshoot). The amount of core overshoot during the main-sequence phase is found to be mild, of the order of 0.1\,$H_{\rm p}$., Comment: Accepted in A&A
Published: 2012
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11. CoRoT's view on variable B8/9 stars: spots versus pulsations. Evidence for differential rotation in HD 174648

Author: Frédéric Baudin, Pieter Degroote, Michel Auvergne, Conny Aerts, Claude Catala, Alfred F. Noels, Eric Michel, Andrea Miglio, D. W. Kurtz, Reza Samadi, Josefina Montalbán, Annie Baglin, Steven Bloemen, Bram Acke, Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 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), Jeremiah Horrocks Institute of Astrophysics, University of Central Lancashire, Institut d'Astrophysique, Géophysique et Océanographie, Université de Liège, Institut d'astrophysique spatiale (IAS), and 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)
Subjects: Physics, 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Astronomy and Astrophysics, Context (language use), Astrophysics, Light curve, 01 natural sciences, Instability, Stars, Photometry (astronomy), Amplitude, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Differential rotation, Astrophysics::Earth and Planetary Astrophysics, Spectroscopy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract: Context. There exist few variability studies of stars in the region in the Hertzsprung-Russell diagram between the A and B-star pulsational instability strips. With the aid of the high precision continuous measurements of the CoRoT space satellite, low amplitudes are more easily detected, making a study of this neglected region worthwhile. Aims. We collected a small sample of B stars observed by CoRoT to determine the origin of the different types of variability observed. Methods. We combine literature photometry and spectroscopy to measure the fundamental parameters of the stars in the sample, and compare asteroseismic modelling of the light curves with (differentially rotating) spotted star models. Results. We found strong evidence for the existence of spots and differential rotation in HD 174648, and formulated hypotheses for their origin. We show that the distinction between pulsations and rotational modulation is difficult to make solely based on the light curve, especially in slowly rotating stars., 16 pages, 18 figures, accepted for publication by Astronomy and Astrophysics
Published: 2011
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12. Plaskett's star: analysis of the CoRoT photometric data

Author: Laurent Mahy, F. Baudin, Gregor Rauw, Pieter Degroote, Reza Samadi, Eric Michel, J. Cuypers, Michel Auvergne, Eric Gosset, Claude Catala, Alfred F. Noels, A. Baglin, Ronny Blomme, Conny Aerts, Mélanie Godart, Thierry Morel, Institut d'Astrophysique, Géophysique et Océanographie, Université de Liège, 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), Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Observatoire Royal de Belgique (ORB), 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), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
Subjects: Physics, 010308 nuclear & particles physics, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Hot spot (veterinary medicine), Astrophysics, Star (graph theory), Light curve, 01 natural sciences, Asteroseismology, Stars, Quality (physics), Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Orbital motion, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Noise (radio)
Abstract: The SRa02 of the CoRoT space mission for Asteroseismology was partly devoted to stars belonging to the Mon OB2 association. An intense monitoring was performed on Plaskett's Star (HD47129) and the unprecedented quality of the light curve allows us to shed new light on this very massive, non-eclipsing binary system. We particularly aimed at detecting periodic variability which might be associated with pulsations or interactions between both components. We also searched for variations related to the orbital cycle which could help to constrain the inclination and the morphology of the binary system. A Fourier-based prewhitening and a multiperiodic fitting procedure were applied to analyse the time series and extract the frequencies of variations. We describe the noise properties to tentatively define an appropriate significance criterion, to only point out the peaks at a certain significance level. We also detect the variations related to the orbital motion and study them by using the NIGHTFALL program. The periodogram exhibits a majority of peaks at low frequencies. Among these peaks, we highlight a list of about 43 values, including notably two different sets of harmonic frequencies whose fundamental peaks are located at about 0.07 and 0.82d-1. The former represents the orbital frequency of the binary system whilst the latter could probably be associated with non-radial pulsations. The study of the 0.07d-1 variations reveals the presence of a hot spot most probably situated on the primary star and facing the secondary. The investigation of this unique dataset constitutes a further step in the understanding of Plaskett's Star. These results provide a first basis for future seismic modelling. The existence of a hot region between both components renders the determination of the inclination ambiguous., Comment: Accepted in A&A, 13 pages, 7 figures, 2 tables
Published: 2011
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13. Amplitudes and lifetimes of solar-like oscillations observed by CoRoT (Corrigendum). Red-giant versus main-sequence stars

Author: Thomas Kallinger, J. De Ridder, C. Barban, Jérôme Ballot, Frédéric Baudin, A. P. Hatzes, Werner W. Weiss, Fabien Carrier, M. J. Goupil, Othman Benomar, Sébastien Deheuvels, Reza Samadi, Saskia Hekker, Thierry Morel, Kevin Belkacem, 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), 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), Institut d'Astrophysique, Géophysique et Océanographie, Université de Liège, Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Institut de recherche en astrophysique et planétologie (IRAP), 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), Thüringer Landessternwarte, Tautenburg Observatory, and Institut für Astronomie, Universität Wien (IfA)
Subjects: Physics, 010308 nuclear & particles physics, Red giant, Astronomy, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Asteroseismology, Stars, Amplitude, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], 0103 physical sciences, Solar-like oscillations, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Main sequence
Abstract: SOURCE (OR PART OF THE FOLLOWING SOURCE): Type article Title Amplitudes and lifetimes of solar-like oscillations observed by CoRoT: redgiant versus main-sequence stars. (Corrigendum) Author(s) F. Baudin, C. Barban, K. Belkacem, S. Hekker, T. Morel, R. Samadi, O. Benomar, M.J. Goupil, F. Carrier, J. Ballot, S. Deheuvels, J. de Ridder, et al. Faculty FNWI: Astronomical Institute Anton Pannekoek (IAP) Year 2011
Published: 2011
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14. Amplitudes of solar p modes: Modelling of the eddy time-correlation function

Author: Reza Samadi, M. J. Goupil, Kevin Belkacem, 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: Convection, Physics, History, Turbulence, Gaussian, Reynolds number, Markov process, FOS: Physical sciences, Function (mathematics), Computer Science Applications, Education, Physics::Fluid Dynamics, symbols.namesake, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Eddy, symbols, Statistical physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: Modelling amplitudes of stochastically excited oscillations in stars is a powerful tool for understanding the properties of the convective zones. For instance, it gives us information on the way turbulent eddies are temporally correlated in a very large Reynolds number regime. We discuss the way the time correlation between eddies is modelled and we present recent theoretical developments as well as observational results. Eventually, we discuss the physical underlying meaning of the results by introducing the Ornstein-Uhlenbeck process, which is a sub-class of a Gaussian Markov process., Comment: GONG 2010 - SoHO 24, A new era of seismology of the Sun and solar-like stars, to be published in the Journal of Physics: Conference Series (JPCS)
Published: 2010
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15. Detection of Solar-like Oscillations from Kepler Photometry of the Open Cluster NGC 6819

Author: Yveline Lebreton, Charles S. Baldner, Jørgen Christensen-Dalsgaard, Juan Carlos Suárez, Andrea Miglio, J. Molenda-Zakowicz, Nada Jevtic, Achim Weiss, Savita Mathur, Marie-Jo Goupil, L. Esch, Saskia Hekker, William J. Borucki, Caroline Barban, Hans Bruntt, Rafael A. García, Daniel Huber, Aldo Serenelli, Ian R. Stevens, Victor Silva Aguirre, Frank Grundah, Vinothini Sangaralingam, Katia Biazzo, Hans Kjeldsen, Torben Arentoft, Christiaan Sterken, Søren Meibom, Ian W. Roxburgh, Jérôme Ballot, Yvonne Elsworth, Karsten Brogaard, Francesca D'Antona, Dennis Stello, Ning Gai, Josefina Montalbán, Christoffer Karoff, Biwei Jiang, Timothy R. Bedding, Sarbani Basu, William J. Chaplin, Ronald L. Gilliland, Timothy M. Brown, B. Mosser, Kevin Belkacem, Róbert Szabó, Jon M. Jenkins, Pierre Demarque, Arlette Noels, Teodoro Roca Cortés, Peter Stine, Reza Samadi, David G. Koch, Sydney Institute for Astronomy (SIfA), The University of Sydney, Department of Astronomy, Yale University [New Haven], 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), 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], Las Cumbres Observatory Global Telescope, Danish AsteroSeismology Centre (DASC), Aarhus University [Aarhus], Space Telescope Science Institute (STSci), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - 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)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-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), Indian Institute of Astrophysics (IIA), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Département des Sciences et Gestion de l'Environnement/Océanologie [Liège], Université de Liège, INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), INAF - Osservatorio Astronomico di Roma (OAR), Beijing Normal University (BNU), 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), Department of Physics and Engineering Technology, Bloomsburg University, Astronomical Institute [Wroclaw], University of Wrocław [Poland] (UWr), Instituto de Astrofisica de Canarias (IAC), Departmento de Astrofísica, Universidad de La Laguna [Tenerife - SP] (ULL), Department of Computer Science (Queen Mary University of London), Queen Mary University of London (QMUL), Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, Vrije Universiteit Brussel (VUB), Konkoly Observatory, Research Centre for Astronomy and Earth Sciences [Budapest], Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA), NASA Ames Research Center (ARC), 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), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Consejo Superior de Investigaciones Científicas [Spain] (CSIC), Beijing Normal University, University of Wrocław [Poland], Vrije Universiteit [Brussels] (VUB), 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), 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), Harvard University-Smithsonian Institution, and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)
Subjects: FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, stars: interiors, 01 natural sciences, Asteroseismology, Luminosity, open clusters and associations: individual: NGC 6819, techniques: photometric, Frequency separation, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Solar-like oscillations, 010303 astronomy & astrophysics, Stellar evolution, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Radial velocity, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, stars: fundamental parameters, stars: oscillations, Open cluster
Abstract: Asteroseismology of stars in clusters has been a long-sought goal because the assumption of a common age, distance and initial chemical composition allows strong tests of the theory of stellar evolution. We report results from the first 34 days of science data from the Kepler Mission for the open cluster NGC 6819 -- one of four clusters in the field of view. We obtain the first clear detections of solar-like oscillations in the cluster red giants and are able to measure the large frequency separation and the frequency of maximum oscillation power. We find that the asteroseismic parameters allow us to test cluster-membership of the stars, and even with the limited seismic data in hand, we can already identify four possible non-members despite their having a better than 80% membership probability from radial velocity measurements. We are also able to determine the oscillation amplitudes for stars that span about two orders of magnitude in luminosity and find good agreement with the prediction that oscillation amplitudes scale as the luminosity to the power of 0.7. These early results demonstrate the unique potential of asteroseismology of the stellar clusters observed by Kepler., Comment: 5 pages, 4 figures, accepted by ApJ (Lett.)
Published: 2010
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16. The red-giant CoRoT target HR 7349

Author: Eric Michel, Claude Catala, Paolo Ventura, Thomas Kallinger, Werner W. Weiss, A. Baglin, F. Baudin, A. P. Hatzes, Fabien Carrier, Reza Samadi, Thierry Morel, Francesca D'Antona, Arlette Noels, P. Eggenberger, Ennio Poretti, Monica Rainer, Andrea Miglio, J. De Ridder, M. Auvergne, C. Barban, Josefina Montalbán, Saskia Hekker, Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 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), Pôle Astronomie du LESIA, 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, 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), INAF-Osservatorio Astronomico di Roma (INAF-OAR), Observatoire Astronomique de l'Université de Genève, Thüringer Landessternwarte, Tautenburg Observatory, Institut für Astronomie, Universität Wien (IfA), and INAF-Osservatorio Astronomico di Brera (INAF-OAB)
Subjects: Physics, Red giant, K-type main-sequence star, Astronomy, Astronomy and Astrophysics, Astrophysics, Light curve, Cosmology, Photometry (optics), Stars, Space and Planetary Science, Solar-like oscillations, Parallax, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; HR 7349 is a bright [ V=5.8] red giant observed by CoRoT in the seismofield of the first long run. The outstanding CoRoT light curve allowed the detection of several solar-like oscillation modes (both radial and non-radial). On top of these seismic constraints, our observational knowledge on HR 7349 benefits as well from a precise parallax and detailed spectroscopic constraints. We present all the observational constraints that are available for the theoretical modelling of this most promising target.
Published: 2010
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17. The solar-like CoRoT target HD 170987: spectroscopic and seismic observations

Author: K. H. Sato, L. Piau, Graham A. Verner, Orlagh Creevey, Ian W. Roxburgh, Reza Samadi, C. Régulo, Patrick Gaulme, Saskia Hekker, Eric Michel, Thierry Appourchaux, Benoit Mosser, Savita Mathur, Dennis Stello, Christoffer Karoff, Hans Bruntt, Daniel Huber, Claude Catala, A. Baglin, William J. Chaplin, Jérôme Ballot, Rafael A. García, David Salabert, Y. P. Elsworth, Michel Auvergne, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), High Altitude Observatory, National Center for Atmospheric Research, 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), 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), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), 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), Universidad de La Laguna [Tenerife - SP] (ULL), School of Physics and Astronomy, University of Birmingham, Sydney Institute for Astronomy (SIfA), and Astronomy Unit, Queen Mary
Subjects: Rotation period, Physics, oscillations [stars], Stellar mass, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Radius, asteroseismology, Rotation, Light curve, Stars, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, individual: HD 170987 [stars], data analysis [methods], Baryon acoustic oscillations, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: The CoRoT mission is in its third year of observation and the data from the second long run in the galactic centre direction are being analysed. The solar-like oscillating stars that have been observed up to now have given some interesting results, specially concerning the amplitudes that are lower than predicted. We present here the results from the analysis of the star HD 170987.The goal of this research work is to characterise the global parameters of HD 170987. We look for global seismic parameters such as the mean large separation, maximum amplitude of the modes, and surface rotation because the signal-to-noise ratio in the observations do not allow us to measure individual modes. We also want to retrieve the stellar parameters of the star and its chemical composition.We have studied the chemical composition of the star using ground-based observations performed with the NARVAL spectrograph. We have used several methods to calculate the global parameters from the acoustic oscillations based on CoRoT data. The light curve of the star has been interpolated using inpainting algorithms to reduce the effect of data gaps. We find power excess related to p modes in the range [400 - 1200]muHz with a mean large separation of 55.2+-0.8muHz with a probability above 95% that increases to 55.9 +-0.2muHz in a higher frequency range [500 - 1250] muHz and a rejection level of 1%. A hint of the variation of this quantity with frequency is also found. The rotation period of the star is estimated to be around 4.3 days with an inclination axis of i=50 deg +20/-13. We measure a bolometric amplitude per radial mode in a range [2.4 - 2.9] ppm around 1000 muHz. Finally, using a grid of models, we estimate the stellar mass, M=1.43+-0.05 Msun, the radius, R=1.96+-0.046 Rsun, and the age ~2.4 Gyr., Comment: 12 pages, 15 figures, accepted for publication in A&A
Published: 2010
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18. Detection of frequency spacings in the young O-type binary HD 46149 from CoRoT photometry

Author: Sergio Simón-Díaz, Ennio Poretti, Maryline Briquet, Claude Catala, Alfred F. Noels, Reza Samadi, Eric Michel, M. Vučković, Michel Auvergne, M. Hareter, Monica Rainer, Conny Aerts, Pieter Degroote, Frédéric Baudin, K. Smolders, Laurent Mahy, R. Oreiro, Annie Baglin, Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 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), Pôle Astronomie du LESIA, 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Instituto de Astrofísica de Canarias (IAC), Institut d'Astrophysique, Géophysique et Océanographie, Université de Liège, INAF-Osservatorio Astronomico di Brera (INAF-OAB), Institut für Astronomie, Universität Wien (IfA), Institut d'astrophysique spatiale (IAS), and 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)
Subjects: Physics, 010308 nuclear & particles physics, Hertzsprung–Russell diagram, Astronomy, FOS: Physical sciences, Binary number, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Light curve, 01 natural sciences, Photometry (optics), symbols.namesake, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, symbols, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Spectroscopy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract: Using the CoRoT space based photometry of the O-type binary HD46149, stellar atmospheric effects related to rotation can be separated from pulsations, because they leave distinct signatures in the light curve. This offers the possibility of characterising and exploiting any pulsations seismologically. Combining high-quality space based photometry, multi-wavelength photometry, spectroscopy and constraints imposed by binarity and cluster membership, the detected pulsations in HD46149 are analyzed and compared with those for a grid of stellar evolutionary models in a proof-of-concept approach. We present evidence of solar-like oscillations in a massive O-type star, and show that the observed frequency range and spacings are compatible with theoretical predictions. Thus, we unlock and confirm the strong potential of this seismically unexplored region in the HR diagram., Comment: 11 pages, 12 figures, accepted for publication in A&A
Published: 2010
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19. Seismic and spectroscopic characterization of the solar-like pulsating CoRoT target HD 49385

Author: Benoit Mosser, F. Pérez Hernández, Michel Auvergne, C. Barban, Frédéric Baudin, Patrick Gaulme, Rafael A. García, Annie Baglin, Thierry Appourchaux, Graham A. Verner, Savita Mathur, S. Deheuvels, Claude Catala, Ian W. Roxburgh, Reza Samadi, Hans Bruntt, C. Régulo, Eric Michel, Patrick Boumier, 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), Astronomy Unit, Queen Mary, Instituto de Astrofísica de Canarias (IAC), Indian Institute of Astrophysics, 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), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / 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-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Galaxies, Etoiles, Physique, Instrumentation (GEPI), and Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: Physics, Field (physics), FOS: Physical sciences, Astronomy and Astrophysics, Angular velocity, Astrophysics, Low frequency, Amplitude, Spitzer Space Telescope, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Satellite, Astrophysics::Earth and Planetary Astrophysics, Spectroscopy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Spectrograph, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: The star HD 49385 is the first G-type solar-like pulsator observed in the seismology field of the space telescope CoRoT. The satellite collected 137 days of high-precision photometric data on this star, confirming that it presents solar-like oscillations. HD 49385 was also observed in spectroscopy with the NARVAL spectrograph in January 2009. Our goal is to characterize HD 49385 using both spectroscopic and seismic data. The fundamental stellar parameters of HD 49385 are derived with the semi-automatic software VWA, and the projected rotational velocity is estimated by fitting synthetic profiles to isolated lines in the observed spectrum. A maximum likelihood estimation is used to determine the parameters of the observed p modes. We perform a global fit, in which modes are fitted simultaneously over nine radial orders, with degrees ranging from l=0 to l=3 (36 individual modes). Precise estimates of the atmospheric parameters (Teff, [M/H], log g) and of the vsini of HD 49385 are obtained. The seismic analysis of the star leads to a clear identification of the modes for degrees l=0,1,2. Around the maximum of the signal (nu=1013 microHz), some peaks are found significant and compatible with the expected characteristics of l=3 modes. Our fit yields robust estimates of the frequencies, linewidths and amplitudes of the modes. We find amplitudes of about 5.6 +/- 0.8 ppm for radial modes at the maximum of the signal. The lifetimes of the modes range from one day (at high frequency) to a bit more than two days (at low frequency). Significant peaks are found outside the identified ridges and are fitted. They are attributed to mixed modes., 13 pages, 14 figures, accepted in A&A
Published: 2010
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20. A fresh look at the seismic spectrum of HD49933: analysis of 180 days of CoRoT photometry

Author: C. Barban, Claude Catala, Graham A. Verner, William J. Chaplin, Reza Samadi, C. Régulo, Thierry Appourchaux, Eric Michel, Savita Mathur, Tiago L. Campante, Michel Auvergne, Frédéric Baudin, Jérôme Ballot, Ian W. Roxburgh, Patrick Gaulme, Annie Baglin, Y. P. Elsworth, Othman Benomar, Benoit Mosser, T. Toutain, Rafael A. García, 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), Danish AsteroSeismology Centre (DASC), School of Physics and Astronomy, University of Birmingham, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), University of Oslo (UiO), Astronomy Unit, Queen Mary, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), 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), 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), Indian Institute of Astrophysics, and Instituto de Astrofísica de Canarias (IAC)
Subjects: Physics, Markov chain, 010308 nuclear & particles physics, Oscillation, Mode (statistics), FOS: Physical sciences, Estimator, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Photometry (astronomy), Stars, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Orbit (dynamics), Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: Solar-like oscillations have now been observed in several stars, thanks to ground-based spectroscopic observations and space-borne photometry. CoRoT, which has been in orbit since December 2006, has observed the star HD49933 twice. The oscillation spectrum of this star has proven difficult to interpret. Thanks to a new timeseries provided by CoRoT, we aim to provide a robust description of the oscillations in HD49933, i.e., to identify the degrees of the observed modes, and to measure mode frequencies, widths, amplitudes and the average rotational splitting. Several methods were used to model the Fourier spectrum: Maximum Likelihood Estimators and Bayesian analysis using Markov Chain Monte-Carlo techniques. The different methods yield consistent result, and allow us to make a robust identification of the modes and to extract precise mode parameters. Only the rotational splitting remains difficult to estimate precisely, but is clearly relatively large (several microHz in size)., 7 pages, 10 figures
Published: 2009
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21. Solar-like oscillations with low amplitude in the CoRoT target HD 181906

Author: Benoit Mosser, Hans Bruntt, Patrick Gaulme, Annie Baglin, F. Pérez Hernández, Y. P. Elsworth, C. Catala, Eric Michel, Thierry Appourchaux, S. J. Jiménez-Reyes, Ian W. Roxburgh, Othman Benomar, Frédéric Baudin, T. Toutain, Michel Auvergne, Graham A. Verner, Rafael A. García, David Salabert, Patrick Boumier, William J. Chaplin, S. Deheuvels, Reza Samadi, C. Régulo, C. Barban, Jérôme Ballot, Savita Mathur, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / 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-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Instituto de Astrofísica de Canarias (IAC), 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), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), 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), 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, Indian Institute of Astrophysics, Astronomy Unit, Queen Mary, and Sydney Institute for Astronomy (SIfA)
Subjects: Physics, Spectral density, FOS: Physical sciences, Astronomy and Astrophysics, Context (language use), Astrophysics, Effective temperature, Rotation, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Differential rotation, Astrophysics::Solar and Stellar Astrophysics, Solar-like oscillations, Baryon acoustic oscillations, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Instrumentation and Methods for Astrophysics (astro-ph.IM), Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: Context: The F8 star HD 181906 (effective temperature ~6300K) was observed for 156 days by the CoRoT satellite during the first long run in the centre direction. Analysis of the data reveals a spectrum of solar-like acoustic oscillations. However, the faintness of the target (m_v=7.65) means the signal-to-noise (S/N) in the acoustic modes is quite low, and this low S/N leads to complications in the analysis. Aims: To extract global variables of the star as well as key parameters of the p modes observed in the power spectrum of the lightcurve. Methods: The power spectrum of the lightcurve, a wavelet transform and spot fitting have been used to obtain the average rotation rate of the star and its inclination angle. Then, the autocorrelation of the power spectrum and the power spectrum of the power spectrum were used to properly determine the large separation. Finally, estimations of the mode parameters have been done by maximizing the likelihood of a global fit, where several modes were fit simultaneously. Results: We have been able to infer the mean surface rotation rate of the star (~4 microHz) with indications of the presence of surface differential rotation, the large separation of the p modes (~87 microHz), and therefore also the ridges corresponding to overtones of the acoustic modes., Comment: Paper Accepted to be published in A&A. 10 Pages, 12 figures
Published: 2009
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22. Non-radial oscillation modes with long lifetimes in giant stars

Author: Fabien Carrier, Thomas Kallinger, Pierre Barge, Saskia Hekker, Werner W. Weiss, A. Baglin, Artie P. Hatzes, Frédéric Baudin, Magali Deleuil, C. Barban, Reza Samadi, Joris De Ridder, M. Auvergne, Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 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), Pôle Astronomie du LESIA, 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, 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), Thüringer Landessternwarte, Tautenburg Observatory, Observatoire Royal de Belgique (ORB), Institut für Astronomie, Universität Wien (IfA), Laboratoire d'Astrophysique de Marseille (LAM), and 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)
Subjects: Physics, Multidisciplinary, Red giant, Bright giant, Stellar collision, Astronomy, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Horizontal branch, Stars, Astrophysics::Solar and Stellar Astrophysics, Stellar structure, Astrophysics::Earth and Planetary Astrophysics, Solar-like oscillations, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Stellar evolution, Astrophysics::Galaxy Astrophysics
Abstract: When main-sequence stars like the Sun near the end of their life, they expand to become oscillating red giants. Such evolved stars could in principle provide stringent tests of stellar theory via analysis of radial and non-radial stellar oscillations. Until now it has been unclear whether non-radial modes are observable at all in red giants. De Ridder et al. now report the presence of both radial and non-radial oscillations in over 300 giant stars. For some red giants, mode lifetimes are of the order of a month. Current stellar evolution theory cannot account for these observations. Towards the end of their lives, stars like the Sun expand greatly to become red giant stars that oscillate. Such evolved stars could provide stringent tests of stellar theory through the analysis of radial and non-radial stellar oscillations. Here, the presence of such oscillations in more than 300 giant stars is reported, with mode lifetimes of some of the giants in the order of a month. Towards the end of their lives, stars like the Sun greatly expand to become red giant stars. Such evolved stars could provide stringent tests of stellar theory, as many uncertainties of the internal stellar structure accumulate with age. Important examples are convective overshooting and rotational mixing during the central hydrogen-burning phase, which determine the mass of the helium core, but which are not well understood1. In principle, analysis of radial and non-radial stellar oscillations can be used to constrain the mass of the helium core. Although all giants are expected to oscillate2, it has hitherto been unclear whether non-radial modes are observable at all in red giants, or whether the oscillation modes have a short or a long mode lifetime3,4,5,6,7, which determines the observational precision of the frequencies. Here we report the presence of radial and non-radial oscillations in more than 300 giant stars. For at least some of the giants, the mode lifetimes are of the order of a month. We observe giant stars with equally spaced frequency peaks in the Fourier spectrum of the time series, as well as giants for which the spectrum seems to be more complex. No satisfactory theoretical explanation currently exists for our observations.
Published: 2009
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23. A closure model for turbulent convection. Application to the excitation of p modes

Author: Friedrich Kupka, Reza Samadi, Marie-Jo Goupil, Frédéric Baudin, Kevin 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), Pôle Astronomie du LESIA, and 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: Convection, Physics, Natural convection, Radiative cooling, Turbulence, K-epsilon turbulence model, Astronomy and Astrophysics, Rayleigh number, Geophysics, Mechanics, Physics::Fluid Dynamics, Convection zone, Space and Planetary Science, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Rayleigh–Bénard convection
Abstract: Oscillations of stellar p modes excited by turbulent convection are investigated. In the uppermost part of the solar convection zone, radiative cooling is responsible for the formation of turbulent plumes, hence the medium is characterized with downdrafts and updrafts. The motivation is to take the asymmetry of up- and downflows created by turbulent plumes into account through an adapted closure model. We built a generalized two-scale mass-flux model (GTFM) that considers both the skew introduced by the presence of two flows and the effect of turbulence onto each flow. In order to apply the GTFM to the solar case, we introduce the plume dynamics as modelled by Rieutord & Zahn (1995) and construct a closure model with plumes (CMP). The CMP enables to express third- and fourth-order velocity correlation products in terms of the second-order ones. When comparing with 3D numerical simulation results, the CMP improves the agreement for the fourth order moments in comparison with the quasi-normal approximation (QNA) or the classical mass-flux model (MFM). This excitation model reproduces the maximum of the power supplied to solar p modes, when compared with GOLF observations.
Published: 2006
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24. A closure model with plumes. I. The solar convection

Author: Reza Samadi, Marie-Jo Goupil, Friedrich Kupka, Kevin 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), Pôle Astronomie du LESIA, 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Max-Planck-Institut für Astrophysik (MPA)
Subjects: Convection, Physics, Turbulence, media_common.quotation_subject, Astrophysics (astro-ph), Skew, FOS: Physical sciences, Astronomy and Astrophysics, Mechanics, Astrophysics, Asymmetry, Plume, Physics::Fluid Dynamics, Convection zone, Space and Planetary Science, Skewness, Astrophysics::Solar and Stellar Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Excitation, media_common
Abstract: Oscillations of stellar p modes, excited by turbulent convection, are investigated. We take into account the asymmetry of the up and downflows created by turbulent plumes through an adapted closure model. In a companion paper, we apply it to the formalism of excitation of solar p modes developed by Samadi & Goupil 2001. Using results from 3D numerical simulations of the upper most part of the solar convection zone, we show that the two-scale-mass-flux model (TFM) is valid only for quasi-laminar or highly skewed flows (Gryanik & Hartmann 2002). We build a generalized-Two-scale-Mass-Flux Model (GTFM) model which takes into account both the skew introduced by the presence of two flows and the effects of turbulence in each flow. In order to apply the GTFM to the solar case, we introduce the plume dynamics as modelled by Rieutord & Zahn (1995) and construct a Closure Model with Plumes (CMP). When comparing with 3D simulation results, the CMP improves the agreement for the fourth order moments, by approximatively a factor of two compared with the use of the quasi-normal approximation or a skewness computed with the classical TFM. The asymmetry of turbulent convection in the solar case has an important impact on the vertical-velocity fourth-order moment which has to be accounted for by models. The CMP is a significant improvement and is expected to improve the modelling of solar p-mode excitation., 13 pages, accepted for publication in A&A
Published: 2006
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25. Rotation profile inversion in solar-like stars. In the COROT framework

Author: Reza Samadi, Marie-Jo Goupil, J. Lochard, 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), 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), Pôle Astronomie du LESIA, 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Ingénieurs, Techniciens et Administratifs
Subjects: Physics, Inverse, Astronomy and Astrophysics, Inversion (meteorology), Astrophysics, Stars, Amplitude, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Random noise, Simulated data, Excited state, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Special care, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; The observation of a few mixed modes on solar-like oscillating stars would enable their rotation profile to be inverted with success. Here simulated data are used to show that it is possible to find models for solar-like stars that present stochastically excited mixed modes with detectable amplitudes. We take special care to build the mode set by computing the mode amplitudes and selecting those modes with amplitudes compatible with the performance of the forthcoming seismic space experiment, COROT. The frequency set is inverted for various cases where input and trial stellar models differ and where random noise is added to the splittings. We show it is possible to localize a rotation gradient and assess its magnitude. Moreover the use of inverse and forward procedures in parallel gives access to a large part of the profile. We provide several constraints to help the selection of such stars. One looks for a relatively evolved star (still on the main sequence) of ~= 1.5 ~ M_&sun; and the rotation rate on the surface should not be too small.
Published: 2005
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26. Effect of Local Treatments of Convection upon the Solar P-Mode Excitation Rates

Author: Davoud-Reza Samadi, Marie-José Goupil, Yveline Lebreton, Veer, C. T., Friedrich Kupka, 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), Pôle Astronomie du LESIA, and 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We compute, for several solar models, the rates P at which the solar radial p modes are expected to be excited. The solar models are computed with two different local treatments of convection : the classical mixing-length theory (MLT hereafter) and Canuto, Goldmann and Mazzitelli(1996, CGM hereafter)'s formulation. For one set of solar models (EMLT and ECGM models), the atmosphere is gray and assumes Eddington's approximation. For a second set of models (KMLT and KCGM models), the atmosphere is built using a T(tau) law which has been obtained from a Kurucz's model atmosphere computed with the same local treatment of convection. The mixing-length parameter in the model atmosphere is chosen so as to provide a good agreement between synthetic and observed Balmer line profiles, while the mixing-length parameter in the interior model is calibrated so that the model reproduces the solar radius at solar age. For the MLT treatment, the rates P do depend significantly on the properties of the atmosphere. On the other hand, for the CGM treatment, differences in P between the ECGM and the KCGM models are very small compared to the error bars attached to the seismic measurements. The excitation rates P for modes from the EMLT model are significantly under-estimated compared with the solar seismic constraints. The KMLT model results in intermediate values for P and shows also an important discontinuity in the temperature gradient and the convective velocity. On the other hand, the KCGM model and the ECGM model yield values for P closer to the seismic data than the EMLT and KMLT models. We conclude that the solar p-mode excitation rates provide valuable constraints and according to the present investigation cleary favor the CGM treatment with respect to the MLT., 4 pages, 3 figures, proceedings of the SOHO14/GONG 2004 workshop "Helio- and Asteroseismology: Towards a Golden Future" from July 12-16 2004 at New Haven CT (USA)
Published: 2004

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26 results on '"Reza Samadi"'

1. Velocity-intensity asymmetry reversal of solar radial p-modes

2. Calibration of mixing-length parameter α for MLT and FST models by matching with CO 5 BOLD models

3. Influence of metallicity on the near-surface effect on oscillation frequencies

4. Dipole modes with depressed amplitudes in red giants are mixed modes

5. Helium signature in red giant oscillation patterns observed by Kepler

6. Solar-like oscillations in distant stars as seen by CoRoT : the special case of HD 42618, a solar sister

7. Seismic diagnostics for transport of angular momentum in stars II. Interpreting observed rotational splittings of slowly rotating red giant stars

8. Spin down of the core rotation in red giants

9. Mode lifetime and associated scaling relations

10. Modelling a high-mass red giant observed by CoRoT

11. CoRoT's view on variable B8/9 stars: spots versus pulsations. Evidence for differential rotation in HD 174648

12. Plaskett's star: analysis of the CoRoT photometric data

13. Amplitudes and lifetimes of solar-like oscillations observed by CoRoT (Corrigendum). Red-giant versus main-sequence stars

14. Amplitudes of solar p modes: Modelling of the eddy time-correlation function

15. Detection of Solar-like Oscillations from Kepler Photometry of the Open Cluster NGC 6819

16. The red-giant CoRoT target HR 7349

17. The solar-like CoRoT target HD 170987: spectroscopic and seismic observations

18. Detection of frequency spacings in the young O-type binary HD 46149 from CoRoT photometry

19. Seismic and spectroscopic characterization of the solar-like pulsating CoRoT target HD 49385

20. A fresh look at the seismic spectrum of HD49933: analysis of 180 days of CoRoT photometry

21. Solar-like oscillations with low amplitude in the CoRoT target HD 181906

22. Non-radial oscillation modes with long lifetimes in giant stars

23. A closure model for turbulent convection. Application to the excitation of p modes

24. A closure model with plumes. I. The solar convection

25. Rotation profile inversion in solar-like stars. In the COROT framework

26. Effect of Local Treatments of Convection upon the Solar P-Mode Excitation Rates

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