References of "Dupret, Marc-Antoine"
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See detailInstability strips of main sequence B stars: a parametric study of iron enhancement
Miglio, Andrea ULg; Bourge, P.-O.; Montalban Iglesias, Josefa ULg et al

in Communications in Asteroseismology (2007), 150

The discovery of beta Cephei stars in low metallicity environments, as well as the difficulty to theoretically explain the excitation of the pulsation modes observed in some beta Cephei and SPB stars ... [more ▼]

The discovery of beta Cephei stars in low metallicity environments, as well as the difficulty to theoretically explain the excitation of the pulsation modes observed in some beta Cephei and SPB stars, suggest that the iron opacity ``bump'' provided by standard models could be underestimated. We investigate, by means of a parametric study, the effect of a local iron enhancement on the location of the beta Cephei and SPB instability strips. [less ▲]

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See detailAn asteroseismic Main Sequence model for the delta Scuti star 44 Tau
Garrido, R.; Suárez, J. C.; Grigahcène, A. et al

in Communications in Asteroseismology (2007), 150

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See detailTwo-scale mass-flux closure models for turbulence: p-mode amplitudes in solar-like stars
Belkacem, Kevin ULg; Samadi, R.; Goupil, Marie-José et al

in Communications in Asteroseismology (2007), 150

A new closure model has been developed, which takes into account both the skewness of the velocity distribution induced by the presence of two flows in the convection zone, and the effects of turbulence ... [more ▼]

A new closure model has been developed, which takes into account both the skewness of the velocity distribution induced by the presence of two flows in the convection zone, and the effects of turbulence onto each flow (Belkacem et al. 2006a). Applied to the formalism of p-mode excitation, it has been possible to validate this theoretical model by a comparison with the observational excitation rates in the solar case using GOLF data (see Belkacem et al. 2006b). The next step is to consider alpha Cen A for which observations of the mode-damping rates are available. [less ▲]

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See detaillambda Boo stars among the gamma Dor-type pulsators: the cases of HD 218427 and HD 239276
Rodríguez, E.; Suárez, J. C.; Moya, A. et al

in Communications in Asteroseismology (2007), 150

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See detailAsteroseismology and mode driving of the Herbig Ae star HD 104237
Dupret, Marc-Antoine ULg; Théado, S.; Böhm, T. et al

in Communications in Asteroseismology (2007), 150

Eight pulsation frequencies were detected in the Herbig Ae star HD 104237 during two observational campaigns in 1999 -- 2000 (Böhm et al. 2004). Moreover, Böhm et al. (in preparation) detected recently in ... [more ▼]

Eight pulsation frequencies were detected in the Herbig Ae star HD 104237 during two observational campaigns in 1999 -- 2000 (Böhm et al. 2004). Moreover, Böhm et al. (in preparation) detected recently in their data two independent signatures of a signal at 95 hr that corresponds probably to rotational modulation. We present here a seismic study of this Pre-Main Sequence star based on these observations. Different possible interpretations of the pulsation spectrum are considered. The driving of the pulsation modes is not explained by standard models, the observed frequencies being too high for delta Scuti-type pulsations. We consider the effect of He accumulation in its partial ionization zones as a possible explanation for this driving. [less ▲]

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See detailSolar-like oscillation amplitudes and line-widths as a probe for turbulent convection in stars
Samadi, R.; Belkacem, Kevin ULg; Goupil, M*-J et al

in IAU Symposium (2007, May 01)

Excitation of solar-like oscillations is attributed to turbulent convection and takes place at the upper-most part of the outer convective zones. Amplitudes of these oscillations depend on the efficiency ... [more ▼]

Excitation of solar-like oscillations is attributed to turbulent convection and takes place at the upper-most part of the outer convective zones. Amplitudes of these oscillations depend on the efficiency of the excitation processes as well as on the properties of turbulent convection. We present past and recent improvements on the modeling of those processes. We show how the mode amplitudes and mode line-widths can bring information about the turbulence in the specific cases of the Sun and Alpha Cen A. [less ▲]

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See detailOscillating blue stragglers, gamma Doradus stars and eclipsing binaries in the open cluster NGC 2506
Arentoft, T.; De Ridder, J.; Grundahl, F. et al

in Astronomy and Astrophysics (2007), 465

Context: This is the first step in a project to combine studies of eclipsing binaries and oscillating stars to probe the interior of Blue Stragglers (BS). This may imply a way to discriminate ... [more ▼]

Context: This is the first step in a project to combine studies of eclipsing binaries and oscillating stars to probe the interior of Blue Stragglers (BS). This may imply a way to discriminate observationally between different birth mechanisms of BS stars. Aims: We study the open cluster NGC 2506 which contains oscillating BS stars and detached eclipsing binaries for which accurate parameters can be derived. This will tightly constrain the cluster isochrone and provide an absolute mass, radius and luminosity-scale for the cluster stars along with the cluster age, metallicity and distance. The present work focuses on obtaining the light curves of the binaries and determine their orbital periods, on obtaining power spectra of the oscillating BS stars to select targets for follow-up studies, and on searching for gamma Doradus type variables which are also expected to be present in the cluster. Methods: With a two-colour, dual-site photometric campaign we obtained 3120 CCD-images of NGC 2506 spread over four months. We analysed the BI time-series of the oscillating stars and used simulations to derive statistical uncertainties of the resulting frequencies, amplitudes and phases. A preliminary mode-identification was performed using frequency ratios for the oscillating BS stars, and amplitude ratios and phase differences for a population of newly detected gamma Doradus stars. Results: We quadrupled the number of known variables in NGC 2506 by discovering 3 new oscillating BS stars, 15 gamma Doradus stars and four new eclipsing binaries. The orbital periods of 2 known, detached eclipsing binaries were derived. We discovered a BS star with both p-mode and g-mode variability and we confronted our gamma Doradus observations with state-of-the-art seismic models, but found significant discrepancy between theory and observations. Conclusions: . NGC 2506 is an excellent target for asteroseismic tests of stellar models, as strong external constraints can be imposed on the models of a population of more than 20 oscillating stars of different types. Based on observations obtained at the Flemish Mercator telescope on La Palma, Spain, the Danish 1.5-m telescope at ESO, La Silla, Chile, and on observations collected at the European Southern Observatory, Paranal, Chile (ESO Programme 075.D-0206(B)). Catalog of individual photometry measurements for all variables is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/465/965 [less ▲]

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See detailCalibration of the pre-main sequence RS Chamaleontis binary system
Alecian, E.; Goupil, Marie-José; Lebreton, Y. et al

in Astronomy and Astrophysics (2007), 465

Context: The calibration of binary systems with accurately known masses and/or radii provides powerful tools to test stellar structure and evolution theory and to determine the age and helium content of ... [more ▼]

Context: The calibration of binary systems with accurately known masses and/or radii provides powerful tools to test stellar structure and evolution theory and to determine the age and helium content of stars. We study the eclipsing double-lined spectroscopic binary system RS Cha, for which we have accurate observations of the parameters of both stars (masses, radii, luminosities, effective temperatures and metallicity). Aims: We have calculated several sets of stellar models for the components of the RS Cha system, with the aim of reproducing simultaneously the available observational constraints and to estimate the age and initial helium abundance of the system. Methods: Using the CESAM stellar evolution code, we model both components starting from the initial mass and metallicity and adjusting the input parameters and physics in order to satisfy the observational constraints. Results: We find that the observations cannot be reproduced if we assume that the abundance ratios are solar but they are satisfied if carbon and nitrogen are depleted in the RS Cha system with respect to the Sun. This is in accordance with the abundances observed in other young stars. The RS Cha system is in an evolutionary stage at the end of the PMS phase where models are not strongly sensitive to various physical uncertainties. However we show that the oscillations of these two stars, which have been detected, would be able to discriminate between different options in the physical description of this evolutionary phase. [less ▲]

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See detailLong term photometric monitoring with the Mercator telescope. Frequencies and mode identification of variable O-B stars
De Cat, P.; Briquet, Maryline ULg; Aerts, C. et al

in Astronomy and Astrophysics (2007), 463

Aims. We selected a large sample of O-B stars that were considered as (candidate) slowly pulsating B, beta Cep, and Maia stars after the analysis of their hipparcos data. We analysed our new seven ... [more ▼]

Aims. We selected a large sample of O-B stars that were considered as (candidate) slowly pulsating B, beta Cep, and Maia stars after the analysis of their hipparcos data. We analysed our new seven passband geneva data collected for these stars during the first three years of scientific operations of the mercator telescope. We performed a frequency analysis for 28 targets with more than 50 high-quality measurements to improve their variability classification. For the pulsating stars, we tried both to identify the modes and to search for rotationally split modes. Methods: We searched for frequencies in all the geneva passbands and colours by using two independent frequency analysis methods and we applied a 3.6 S/N-level criterion to locate the significant peaks in the periodograms. The modes were identified by applying the method of photometric amplitudes for which we calculated a large, homogeneous grid of equilibrium models to perform a pulsational stability analysis. When both the radius and the projected rotational velocity of an object are known, we determined a lower limit for the rotation frequency to estimate the expected frequency spacings in rotationally split pulsation modes. Results: We detected 61 frequencies, among which 33 are new. We classified 21 objects as pulsating variables (7 new confirmed pulsating stars, including 2 hybrid beta Cep/SPB stars), 6 as non-pulsating variables (binaries or spotted stars), and 1 as photometrically constant. All the Maia candidates were reclassified into other variability classes. We performed mode identification for the pulsating variables for the first time. The most probable l value is 0, 1, 2, and 4 for 1, 31, 9, and 5 modes, respectively, including only 4 unambiguous identifications. For 7 stars we cannot rule out that some of the observed frequencies belong to the same rotationally split mode. For 4 targets we may begin to resolve close frequency multiplets. Based on observations collected with the p7 photometer attached to the Flemish 1.2-m mercator telescope situated at the Roque de los Muchachos observatory on La Palma (Spain). Section [see full textsee full text], including Figs. is only available in electronic form at http://www.aanda.org, and Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/463/243 [less ▲]

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See detailInstability strips of slowly pulsating B stars and beta Cephei stars: the effect of the updated OP opacities and of the metal mixture
Miglio, Andrea ULg; Montalban Iglesias, Josefa ULg; Dupret, Marc-Antoine ULg

in Monthly Notices of the Royal Astronomical Society (2007), 375

The discovery of beta Cephei stars in low-metallicity environments, as well as the difficulty in theoretically explaining the excitation of the pulsation modes observed in some beta Cephei and hybrid ... [more ▼]

The discovery of beta Cephei stars in low-metallicity environments, as well as the difficulty in theoretically explaining the excitation of the pulsation modes observed in some beta Cephei and hybrid slowly pulsating B-beta Cephei pulsators, suggest that the `iron opacity bump' provided by stellar models could be underestimated. We analyze the effect of uncertainties in the opacity computations and in the solar metal mixture on the excitation of pulsation modes in B-type stars. We carry out a pulsational stability analysis for four grids of main-sequence models with masses between 2.5 and 12M[SUB]solar[/SUB] computed with OPAL and OP opacity tables and two different metal mixtures. We find that in a typical beta Cephei model the OP opacity is 25 per cent larger than OPAL in the region where the driving of pulsation modes occurs. Furthermore, the difference in the Fe mass fraction between the two metal mixtures considered is of the order of 20 per cent. The implication on the excitation of pulsation modes is non-negligible: the blue border of the slowly pulsating B star (SPB) instability strip is displaced at higher effective temperatures, leading to a larger number of models being hybrid SPB-beta Cephei pulsators. Moreover, higher overtone p-modes are excited in beta Cephei models and unstable modes are found in a larger number of models for lower metallicities, in particular beta Cephei pulsations are also found in models with Z = 0.01. [less ▲]

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See detailAn asteroseismic study of the β cephei star θ ophiuchi : constraints on global stellar parameters and core overshooting
Briquet, Maryline ULg; Morel, Thierry ULg; Thoul, Anne ULg et al

in Monthly Notices of the Royal Astronomical Society (2007), 381(4), 1482-1488

We present a seismic study of the beta Cephei star theta Ophiuchi. Our analysis is based on the observation of one radial mode, one rotationally split l = 1 triplet and three components of a rotationally ... [more ▼]

We present a seismic study of the beta Cephei star theta Ophiuchi. Our analysis is based on the observation of one radial mode, one rotationally split l = 1 triplet and three components of a rotationally split l = 2 quintuplet for which the m values were well identified by spectroscopy. We identify the radial mode as fundamental, the triplet as p(1) and the quintuplet as g(1). Our non-local thermodynamic equilibrium abundance analysis results in a metallicity and CNO abundances in full agreement with the most recent updated solar values. With X epsilon [0.71, 0.7211] and Z epsilon [0.009, 0.015], and using the Asplund et al. mixture but with a Ne abundance about 0.3 dex larger, the matching of the three independent modes enables us to deduce constrained ranges for the mass (M = 8.2 +/- 0.3 M circle dot) and central hydrogen abundance (X-c = 0.38 +/- 0.02) of theta Oph and to prove the occurrence of core overshooting (alpha(ov) = 0.44 +/- 0.07). We also derive an equatorial rotation velocity of 29 +/- 7 km s(-1). Moreover, we show that the observed non-equidistance of the l = 1 triplet can be reproduced by the second-order effects of rotation. Finally, we show that the observed rotational splitting of two modes cannot rule out a rigid rotation model. [less ▲]

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See detailTheoretical aspects of g-mode pulsations in $\gamma$ Doradus stars
Dupret, Marc-Antoine ULg; Miglio, Andrea ULg; Grigahcène, A. et al

in Communications in Asteroseismology (2007), 150

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See detailTime Dependent Convection vs. Frozen Convection Approximations
Grigahcène, A.; Dupret, Marc-Antoine ULg; Garrido, R.

in EAS Publications Series (2007)

The approximation known as Frozen Convection has been widely used in the context of stellar oscillations due to the lack of a Time Dependent Convection theory. This approximation supposes to neglect the ... [more ▼]

The approximation known as Frozen Convection has been widely used in the context of stellar oscillations due to the lack of a Time Dependent Convection theory. This approximation supposes to neglect the interaction between convection and oscillations and there are different ways to do it. The choice can affect theoretical predictions concerning the non-adiabatic treatment of the stellar oscillations. In fact, fictitious excitation or damping of the pulsation modes can be produced depending on the approximation used. [less ▲]

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See detailImpact of Transport and Dynamical Processes Upon Stellar Oscillation Frequencies
Goupil, M. J.; Dupret, Marc-Antoine ULg

in EAS Publications Series (2007)

In order to prepare the theoretical interpretation of the oscillation frequencies detected by CoRoT, comparisons of results from standard stellar models by the ESTA group have proven to be very useful ... [more ▼]

In order to prepare the theoretical interpretation of the oscillation frequencies detected by CoRoT, comparisons of results from standard stellar models by the ESTA group have proven to be very useful. The next issue which is briefly addressed here is ``what are the additional physical processes that must be included in stellar models computed with different evolutionary codes for the next comparison exercises?'' We therefore discuss the impact on oscillation frequencies of several physical processes which are still poorly understood and/or poorly modelled but cannot be fully discarded. [less ▲]

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See detailThe Seismology Programme of CoRoT
Michel, Eric; Baglin, A.; Auvergne, M. et al

in Proceedings of "The CoRoT Mission Pre-Launch Status - Stellar Seismology and Planet Finding (2006, November 01)

We introduce the main lines and specificities of the CoRoT Seismology Core Programme. The development and consolidation of this programme has been made in the framework of the CoRoT Seismology Working ... [more ▼]

We introduce the main lines and specificities of the CoRoT Seismology Core Programme. The development and consolidation of this programme has been made in the framework of the CoRoT Seismology Working Group. With a few illustrative examples, we show how CoRoT data will help to address various problems associated with present open questions of stellar structure and evolution. [less ▲]

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See detailRotational Splittings with CoRoT, Expected Number of Detections and Measurement Accuracy
Goupil, M. J.; Lochard, J.; Samadi, R. et al

in ESA Special Publication (2006, November 01)

One of the main goal of the CoRoT experiment is to determine the internal rotation of stars. A seismic measure of rotation requires the detection and an accurate measurement of rotational splittings. Our ... [more ▼]

One of the main goal of the CoRoT experiment is to determine the internal rotation of stars. A seismic measure of rotation requires the detection and an accurate measurement of rotational splittings. Our ability to achieve this goal with CoRoT observations depends on the properties of the target star (in short: spectral type and distance) and will be discussed. [less ▲]

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See detailWhy Bothering to Measure Stellar Rotation with CoRoT?
Goupil, Marie-José; Moya, A.; Suarez, J. C. et al

in ESA Special Publication (2006, November 01)

One important goal of the CoRoT experiment is to obtain information about the internal rotation of stars, in particular the ratio of central to surface rotation rates. This will provide constraints on the ... [more ▼]

One important goal of the CoRoT experiment is to obtain information about the internal rotation of stars, in particular the ratio of central to surface rotation rates. This will provide constraints on the modelling of transport mechanisms of angular momentum acting in radiative (rotationally induced turbulent) and convective zones (plumes, extension beyond convectively instable regions). Relations between the surface rotation period and age, magnetic activity, mass loss and other stellar characteristics can also be studied with a statistically significant set of data as will be provided by Corot. We present various theoretical efforts performed over the past years in order to develope the theoretical tools which will enable us to study rotation with Corot. [less ▲]

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See detailModelling intermediate mass red giants
Moreira, O.; Noels-Grötsch, Arlette ULg; Dupret, Marc-Antoine ULg

in Proceedings of SOHO 18/GONG 2006/HELAS I, Beyond the spherical Sun (2006, October 01)

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See detailEnergetic effects in classical pulsators
Dupret, Marc-Antoine ULg; Grigahcène, A.; Théado, S. et al

in Proceedings of SOHO 18/GONG 2006/HELAS I, Beyond the spherical Sun (2006, October 01)

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