References of "Garrido, R"
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See detailTowards Precise Asteroseismology of Solar-Like Stars
Grigahcène, A.; Dupret, Marc-Antoine ULg; Sousa, S. G. et al

in Astrophysics and Space Science Proceedings series (2013), 31

Adiabatic modeling of solar-like oscillations cannot exceed a certain level of precision for fitting individual frequencies. This is known as the problem of near-surface effects on the mode physics. We ... [more ▼]

Adiabatic modeling of solar-like oscillations cannot exceed a certain level of precision for fitting individual frequencies. This is known as the problem of near-surface effects on the mode physics. We present a theoretical study which addresses the problem of frequency precision in non-adiabatic models using a time-dependent convection treatment. We find that the number of acceptable model solutions is significantly reduced and more precise constraints can be imposed on the models. Results obtained for a specific star (β Hydri) lead to very good agreement with both global and local seismic observables. This indicates that the accuracy of model fitting to seismic data is greatly improved when a more complete description of the interaction between convection and pulsation is taken into account. [less ▲]

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See detailSuccessful Asteroseismology for a Better Characterization of the Exoplanet HAT-P-7b
Oshagh, M.; Grigahcène, A.; Benomar, O. et al

in Astrophysics and Space Science Proceedings (2013), 31

It is well known that asteroseismology is the unique technique permitting the study of the internal structure of pulsating stars using their pulsational frequencies, which is per se very important. It ... [more ▼]

It is well known that asteroseismology is the unique technique permitting the study of the internal structure of pulsating stars using their pulsational frequencies, which is per se very important. It acquires an additional value when the star turns out to be a planet host. In this case, the asteroseismic study output may be a very important input for the study of the planetary system. With this in mind, we use the large time-span of the Kepler public data obtained for the star system HAT-P-7, first to perform an asteroseismic study of the pulsating star using Time-Dependent-Convection (TDC) models. Secondly, we make a revision of the planet properties in the light of the asteroseismic study. [less ▲]

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See detailTowards an effective asteroseismology of solar-like stars: time-dependent convection effects on pulsation frequencies
Grigahcène, A.; Dupret, Marc-Antoine ULg; Sousa, S. G. et al

in Monthly Notices of the Royal Astronomical Society (2012), 422

Since the early days of helioseismology, adiabatic models have shown their limits for a precise fitting of individual oscillation frequencies. This discrepancy, which also exists for solar-type stars, is ... [more ▼]

Since the early days of helioseismology, adiabatic models have shown their limits for a precise fitting of individual oscillation frequencies. This discrepancy, which also exists for solar-type stars, is known to originate near the surface superadiabatic convective region where the interaction between oscillations and convection is likely to have a large effect on the frequencies. We present an asteroseismic study to address the adequacy of time-dependent convection (TDC) non-adiabatic models to better reproduce the observed individual frequencies. We select, for this purpose, three solar-like stars, in addition to the Sun, to which we fit the observed frequencies in a grid of TDC non-adiabatic models. The best model selection is done by applying a maximum likelihood method. The results are compared to pure adiabatic and near-surface corrected adiabatic models. We show that, first, TDC models give very good agreement for the mode frequencies and average lifetimes. In the solar case, the frequency discrepancy is reduced to <1.75 μHz over 95 per cent of the modes considered. Secondly, TDC models give an asteroseismic insight into the usually unconstrained ad hoc stellar parameters, such as the mixing-length parameter α[SUB]MLT[/SUB]. [less ▲]

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See detailGround-based observations of the beta Cephei CoRoT main target HD 180 642: abundance analysis and mode identification
Briquet, Maryline ULg; Uytterhoeven, K.; Morel, Thierry ULg et al

in Astronomy and Astrophysics (2009), 506

The known β Cephei star HD 180 642 was observed by the CoRoT satellite in 2007. From the very high-precision light curve, its pulsation frequency spectrum could be derived for the first time (Degroote ... [more ▼]

The known β Cephei star HD 180 642 was observed by the CoRoT satellite in 2007. From the very high-precision light curve, its pulsation frequency spectrum could be derived for the first time (Degroote and collaborators). In this paper, we obtain additional constraints for forthcoming asteroseismic modeling of the target. Our results are based on both extensive ground-based multicolour photometry and high-resolution spectroscopy. We determine T_eff = 24 500± 1000 K and log g = 3.45± 0.15 dex from spectroscopy. The derived chemical abundances are consistent with those for B stars in the solar neighbourhood, except for a mild nitrogen excess. A metallicity Z = 0.0099± 0.0016 is obtained. Three modes are detected in photometry. The degree â is unambiguously identified for two of them: â = 0 and â = 3 for the frequencies 5.48694 d[SUP]-1[/SUP] and 0.30818 d[SUP]-1[/SUP], respectively. The radial mode is non-linear and highly dominant with an amplitude in the U-filter about 15 times larger than the strongest of the other modes. For the third frequency of 7.36673 d[SUP]-1[/SUP] found in photometry, two possibilities remain: â = 0 or 3. In the radial velocities, the dominant radial mode presents a so-called stillstand but no clear evidence of the existence of shocks is observed. Four low-amplitude modes are found in spectroscopy and one of them, with frequency 8.4079 d[SUP]-1[/SUP], is identified as (â ,m)=(3,2). Based on this mode identification, we finally deduce an equatorial rotational velocity of 38± 15 km s[SUP]-1[/SUP]. Based on data gathered with the 1.2m Mercator telescope Roque de los Muchachos, La Palma, the 90cm telescope at Sierra Nevada Observatory, Spain, the 1.5 m telescope at San Pedro Mártir Observatory, Mexico, the 1m RCC and 50 cm telescope at the PiszkéstetÅ Mountain Station of Konkoly Observatory, Hungary, the 2.2 m ESO telescope (ESO Programme 077.D-0311; ESO Large Programme 178.D-0361) at La Silla, Chile, the 1.93 m and 1.52 m telescopes at the Haute-Provence Observatory, France. Current address: Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot; CEA, IRFU, SAp, centre de Saclay, 91191 Gif-sur-Yvette, France. [less ▲]

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See detailAn asteroseismic study of the beta Cephei CoRoT main target HD 180642: results from the ground-based campaign
Briquet, Maryline ULg; Uytterhoeven, K.; Morel, Thierry ULg et al

in American Institute of Physics Conference Series (2009, September 01)

The β Cephei star HD 180642 was observed by the CoRoT satellite during a run of 156 days in 2007. The space white light photometry revealed the rich frequency spectrum of the star (Degroote et al. 2009 ... [more ▼]

The β Cephei star HD 180642 was observed by the CoRoT satellite during a run of 156 days in 2007. The space white light photometry revealed the rich frequency spectrum of the star (Degroote et al. 2009). In the present study, we provide additional information on the target, based on both ground-based multi-colour photometry and high-resolution spectroscopy. We place our object in the (T[SUB]eff[/SUB], log g) diagram. In addition, we derive the chemical abundances of several elements as well as the metallicity of HD 180642. Finally, we put constraints on the identification of some modes. All these observational constraints will be used to compute stellar models of the target. [less ▲]

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See detailGround-based observations of the beta Cephei CoRoT main target HD 180642
Briquet, Maryline ULg; Uytterhoeven, K.; Aerts, C. et al

in Communications in Asteroseismology (2009), 158

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD~180642. Besides the non-linear dominant ... [more ▼]

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD~180642. Besides the non-linear dominant radial mode several low-amplitude modes are detected in both kinds of datasets. Our aim is to derive the wavenumbers (â ,m) of these modes, as additional constraints to the CoRoT pulsation frequencies, for forthcoming asteroseismic modelling of the star. [less ▲]

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See detailFirst asteroseismic results from CoRoT
Michel, Eric; Baglin, A.; Weiss, W. W. et al

in Communications in Asteroseismology (2008), 156

About one year after the end of the first observational run and six months after the first CoRoT data delivery, we comment the data exploitation progress for different types of stars. We consider first ... [more ▼]

About one year after the end of the first observational run and six months after the first CoRoT data delivery, we comment the data exploitation progress for different types of stars. We consider first results to illustrate how these data of unprecedented quality shed a new light on the field of stellar seismology. [less ▲]

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See detailGround-based observations of the beta Cephei CoRoT main target HD 180642
Briquet, Maryline ULg; Uytterhoeven, K.; Aerts, C. et al

Conference (2008, July)

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD 180642. Besides the non-linear dominant ... [more ▼]

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD 180642. Besides the non-linear dominant radial mode several low-amplitude modes are detected in both kinds of datasets. Our aim is to derive the wavenumbers (ℓ,m) of these modes, as additional constraints to the CoRoT pulsation frequencies, for forthcoming asteroseismic modelling of the star. [less ▲]

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See detailFirst asteroseismic results from CoRoT
Michel, Eric; Baglin, Annie; Weiss, W.W. et al

in Communication in Asteroseismology (2008), 157

About one year after the end of the first observational run and six months after the first CoRoT data delivery, we comment the data exploitation progress for different types of stars. We consider first ... [more ▼]

About one year after the end of the first observational run and six months after the first CoRoT data delivery, we comment the data exploitation progress for different types of stars. We consider first results to illustrate how these data of unprecedented quality shed a new light on the field of stellar seismology. [less ▲]

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See detailA procedure for modelling asymptotic g-mode pulsators: The case of gamma Doradus stars
Moya, A.; Suárez, J. C.; Martín-Ruiz, S. et al

in Astronomische Nachrichten (2008), 329

Mode identification is one of the first and main problems we encounter in trying to develop the complete potential of asteroseismology. In the particular case of {g}-mode pulsators, this is still an ... [more ▼]

Mode identification is one of the first and main problems we encounter in trying to develop the complete potential of asteroseismology. In the particular case of {g}-mode pulsators, this is still an unsolved problem, from both the observational and theoretical points of view. Nevertheless, in recent years, some observational and theoretical efforts have been made to find a solution. In this work we use the latest theoretical and computational tools to understand asymptotic {g}-mode pulsators: 1) the Frequency Ratio Method, and 2) Time Dependent Convection. With these tools, a self-consistent procedure for mode identification and modelling of these {g}-mode pulsators can be constructed. This procedure is illustrated using observational information available for the gamma Doradus star 9 Aurigae. [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 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 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 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 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 detailConvection-pulsation interaction: theories and applications
Dupret, Marc-Antoine ULg; Grigahcene, A.; Gabriel, Maurice ULg et al

in Communications in Asteroseismology (2006), 147

The problem of the interaction between convection and pulsations is considered. A precise modeling of this interaction is required for the seismic study of stars with non-negligible convective envelope ... [more ▼]

The problem of the interaction between convection and pulsations is considered. A precise modeling of this interaction is required for the seismic study of stars with non-negligible convective envelope. After a short introduction to the Time-Dependent Convection theory of Gabriel (1996) and Grigahcene et al. (2005), we give a summary of the main results obtained with this treatment for delta Sct, gamma Dor and solar-like stars. [less ▲]

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See detailFirst unambiguous asteroseismologic modelling of a gamma Doradus star
Moya, A.; Grigahcene, A.; Suárez, J. C. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2006), 77

An asteroseismologic model of the gamma Dor star 9 Aurigae is discussed in this work. This is the first time a complete asteroseismologic scheme for analyzing gamma Dor stars is applied. From standard ... [more ▼]

An asteroseismologic model of the gamma Dor star 9 Aurigae is discussed in this work. This is the first time a complete asteroseismologic scheme for analyzing gamma Dor stars is applied. From standard photometric observations (at least three oscillation frequencies, a photometric error box in the HR diagram and multicolor photometric observations, in this case in the Strömgren system) we can reduce the possible theoretical models for this star, providing constraints to the stellar parameters as mass, overshooting, metallicity, MLT parameter alpha , Brunt-Väiälä integral (I[SUB]th[/SUB]), etc. Simultaneously, an estimate of the modal identification of the observed frequencies is also obtained. This can be possible by the application, for the first time, of a complete procedure where different theoretical and computational techniques, recently developed, are linked and compared with photometric observations. The Frequency Ratio Method (FRM) and the Time Dependent Convection (TDC) theory are the basis of this complete procedure. [less ▲]

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See detailTheoretical Aspects of g-mode Pulsations in gamma Doradus Stars
Dupret, Marc-Antoine ULg; Grigahcène, A.; Garrido, R. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2006), 77

gamma Dor stars are main sequence variable A-F stars whose long periods (between 0.35 and 3 days) correspond to high-order gravity modes pulsation. Most of them are multiperiodic. We will concentrate here ... [more ▼]

gamma Dor stars are main sequence variable A-F stars whose long periods (between 0.35 and 3 days) correspond to high-order gravity modes pulsation. Most of them are multiperiodic. We will concentrate here on two theoretical aspects of these stars. First, an analysis of the driving mechanism of the gamma Dor g-modes is presented, using the linear Time-Dependent Convection (TDC) treatment of Gabriel \cite{Gabriel1996} and Grigahcène et al. \cite{Grigahcene}. This driving is due to a periodic flux blocking mechanism at the base of their convective envelope. The location of the blue and red edges of their instability strip as well as the periods range of their observed modes is explained by the balance between this driving mechanism and radiative damping in the g-mode cavity. Secondly, the multi-color photometric amplitude ratios and the phase differences between the light and velocity curves are considered. It is shown that the agreement between theory and observations obtained with TDC models is much better than with Frozen Convection (FC) models. The theoretical analysis of these observables makes the photometric identification of the degree l of the modes possible and gives constraints on the characteristics of the convective envelope of these stars. Finally, the attractive potential of gamma Dor stars as targets for asteroseismology is considered. [less ▲]

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See detailApplication of time-dependent convection models to the photometric mode identification in gamma Doradus stars
Dupret, Marc-Antoine ULg; Grigahcène, A.; Garrido, R. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2006), 77

We apply the Time-Dependent Convection (TDC) treatment of Gabriel \cite{Gabriel1996} and Grigahcène et al. \cite{Grigahcene} to the photometric mode identification in gamma Dor stars. Comparison of our ... [more ▼]

We apply the Time-Dependent Convection (TDC) treatment of Gabriel \cite{Gabriel1996} and Grigahcène et al. \cite{Grigahcene} to the photometric mode identification in gamma Dor stars. Comparison of our theoretical results with the observed amplitudes and phases of the star gamma Dor is presented. This comparison makes the identification of the degree l of its pulsation modes possible and shows that our TDC models better agree with observations than Frozen Convection (FC) models. [less ▲]

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See detailInfluence of overshooting and metallicity on the delta Scuti and gamma Doradus instability strips
Grigahcène, A.; Dupret, Marc-Antoine ULg; Garrido, R. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2006), 77

Computations of theoretical instability strips (IS) for delta Scuti (Sct) and gamma Dor (Dor) stars are presented. The Time-Dependent Convection (TDC) theory of Gabriel (1996) and Grigahcène et al. (2005 ... [more ▼]

Computations of theoretical instability strips (IS) for delta Scuti (Sct) and gamma Dor (Dor) stars are presented. The Time-Dependent Convection (TDC) theory of Gabriel (1996) and Grigahcène et al. (2005) is adopted in our models. We are able to obtain the delta Sct and gamma Dor IS. We present a prospective study on the influence of the overshooting and metallicity on the location of these IS in the HR diagram. [less ▲]

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