References of "Dupret, Marc-Antoine"
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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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See detailTheoretical damping rates and phase-lags for solar-like oscillations
Dupret, Marc-Antoine ULg; Barban, C.; Goupil, Marie-José et al

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

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See detailA non-local MLT treatment fitting 3D simulations
Dupret, Marc-Antoine ULg; Goupil, M*-J; Samadi, R. et al

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

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See detailAsteroseismology of the new multiperiodic gamma Dor variable HD 239276
Rodríguez, E.; Costa, V.; Zhou, A*-Y et al

in Astronomy and Astrophysics (2006), 456

The variability of HD 239276 was suspected photometrically nearly twenty years ago, but was confirmed with new observations obtained in 2001 during a two-site photometric campaign carried out from Spain ... [more ▼]

The variability of HD 239276 was suspected photometrically nearly twenty years ago, but was confirmed with new observations obtained in 2001 during a two-site photometric campaign carried out from Spain, in uvbybeta Strömgren-Crawford photometry, and China, using the Johnson V filter. Two low-dispersion spectra were also collected. The results establish this star as a new multiperiodic gamma Dor-type pulsator with deficiency in metallicity. Its possible lambda Boo nature is discussed. The frequency analysis shows three pulsational frequencies as significant, but some more are probably present among the residuals. The method based on phase shifts and amplitude ratios in multicolour photometry is used to identify the excited modes with non-adiabatic time-dependent convection models. A very good agreement between the theoretical and observed amplitude ratios is obtained and the two main modes are identified as l=1 modes. Nevertheless, our results do not allow us to discriminate between a solar abundance and a metal deficient nature for this star. The frequency ratio method is further used for the identification of the modes. The results suggest low metallicity for this star, but a lambda Boo nature may be not ruled out. [less ▲]

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See detailThe frequency ratio method and the new multiperiodic gamma Doradus star HD 218427
Rodríguez, E.; Amado, P. J.; Suárez, J. C. et al

in Astronomy and Astrophysics (2006), 450

Oscillations of gamma Dor-type were discovered in the star HD 218427 through simultaneous uvby photometric observations carried out in the year 2003. A few Hbeta-Crawford measurements were also collected ... [more ▼]

Oscillations of gamma Dor-type were discovered in the star HD 218427 through simultaneous uvby photometric observations carried out in the year 2003. A few Hbeta-Crawford measurements were also collected for calibration purposes and they locate this star well inside the gamma Dor instability region. We find HD 218427 to be deficient in metals, similar to other well-defined gamma Dor stars, and discuss the possibility that it has a lambda Boo nature. We carried out frequency analysis for different filters, including the combined "vby" filter, and five frequencies were found as significant with periods ranging between 0.3 and 0.8 days. The recently-developed frequency ratio method is used in order to identify the excited modes. The results are consistent with an l=2 identification for all the modes and with high radial quantum numbers (nË 40) for the three main observed periodicities. The possibility of multiplet structures is also discussed. However, no consistency is found when using the time-dependent convection treatment to discriminate modes. This disagreement can be due to the large rotation velocity taking place in HD 218427 and, consequently, the significant coupling between the modes. [less ▲]

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See detailAnalysis of MERCATOR data - Part I: variable B stars
De Cat, P.; Briquet, Maryline ULg; Aerts, C. et al

in Communications in Asteroseismology (2006), 147

We re-classified 31 variable B stars which were observed more than 50 times in the Geneva photometric system with the p7 photometer attached to the MERCATOR telescope (La Palma) during its first 3 years ... [more ▼]

We re-classified 31 variable B stars which were observed more than 50 times in the Geneva photometric system with the p7 photometer attached to the MERCATOR telescope (La Palma) during its first 3 years of scientific observations. HD 89688 is a possible beta Cephei/slowly pulsating B star hybrid and the main mode of the COROT target HD 180642 shows non-linear effects. The Maia candidates are re-classified as either ellipsoidal variables or spotted stars. Although the mode identification is still ongoing, all the well-identified modes so far have l <= 2. [less ▲]

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See detailThe epsilon-mechanism in PMS and MS delta Scuti stars
Lenain, G.; Scuflaire, Richard ULg; Dupret, Marc-Antoine ULg et al

in Communications in Asteroseismology (2006), 147

Delta Scuti type stars are known to pulsate in nonradial low-order p and g modes. These oscillation modes are driven by the so-called kappa-mechanism involving the second helium ionization zone. However ... [more ▼]

Delta Scuti type stars are known to pulsate in nonradial low-order p and g modes. These oscillation modes are driven by the so-called kappa-mechanism involving the second helium ionization zone. However, since g modes have significant amplitudes near the stellar core, their excitation might be influenced by the epsilon-mechanism which is associated to the nuclear energy production. We investigate the effect of the epsilon-mechanism on the stability of oscillation modes in 1.5 M(solar) pre-main sequence and main sequence stars. [less ▲]

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See detailInstability strip for pre-main-sequence stars
Grigahcene, A.; Dupret, Marc-Antoine ULg; Garrido, R. et al

in Communications in Asteroseismology (2006), 147

We apply the Time Dependent Convection (TDC) treatment presented in Grigahcene et al. (2005) to the study of Pre-main sequence pulsating stars. The stabilization of the p-modes at the red edge of the ... [more ▼]

We apply the Time Dependent Convection (TDC) treatment presented in Grigahcene et al. (2005) to the study of Pre-main sequence pulsating stars. The stabilization of the p-modes at the red edge of the Instability Strip (IS) is obtained by our models. The theoretical IS obtained with Mixing Length (ML) parameter alpha=1.8 is compared to observations and a good agreement is obtained. [less ▲]

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See detailNon-local time-dependent treatments of convection in A-G type stars
Dupret, Marc-Antoine ULg; Samadi, R.; Grigahcene, A. et al

in Communications in Asteroseismology (2006), 147

Time-Dependent Convection (TDC) models obtained by combining the local treatment of Gabriel (1996) and Grigahcene et al. (2005) and the non-local prescriptions of Spiegel (1963) are presented. We show ... [more ▼]

Time-Dependent Convection (TDC) models obtained by combining the local treatment of Gabriel (1996) and Grigahcene et al. (2005) and the non-local prescriptions of Spiegel (1963) are presented. We show that in the stationary unperturbed case, these non-local treatments can be constrained by the results of 3D hydrodynamic simulations (Stein & Nordlund 1998). We consider here the case of solar-type stars with a large convective envelope and A-F type stars with two very thin surface convection zones. [less ▲]

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See detailSeismic study of the Herbig Ae star HD 104237
Dupret, Marc-Antoine ULg; Böhm, T.; Goupil, Marie-José et al

in Communications in Asteroseismology (2006), 147

HD 104237 is the brightest Herbig Ae star, and as such a pre-main sequence (PMS) star. It is also a spectroscopic binary with determined orbital parameters. It was observed in 1999-2000 at SAAO and Mt ... [more ▼]

HD 104237 is the brightest Herbig Ae star, and as such a pre-main sequence (PMS) star. It is also a spectroscopic binary with determined orbital parameters. It was observed in 1999-2000 at SAAO and Mt Stromolo and 1888 Echelle spectra were obtained. From these observations, 8 pulsation frequencies were detected among which 5 with very high confidence (Böhm et al. 2004). We present here a preliminary seismic study based on these observations. We also consider the problem of the excitation of the observed modes and show, as an important result of our study, that HD 104237 is not a delta Sct type pulsator. [less ▲]

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