References of "De Ridder, J."
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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 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 detailApplication of time-dependent convection models to the photometric mode identification in delta Scuti 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 \cite{Grigahcene} to the mode identification and seismic study of delta Sct stars. We compare the non ... [more ▼]

We apply the Time-Dependent Convection (TDC) treatment of Gabriel \cite{Gabriel1996} and Grigahcène \cite{Grigahcene} to the mode identification and seismic study of delta Sct stars. We compare the non-adiabatic phase-lags obtained with TDC and Frozen Convection (FC) treatments and show that they are very different at the red side of the instability strip. Finally, we compare the phase differences between light and velocity curves observed for the star 1 Mon with the theoretical predictions of TDC and FC models. The much better agreement found with the TDC models enables us to identify the modes of this star with a higher degree of confidency. [less ▲]

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See detailObservational results for northern and southern (candidate) gamma Doradus stars .
De Cat, P.; Goossens, K.; Bouckaert, F. et al

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

We report on observational results obtained for 78 objects originally classified as bona-fide or candidate gamma Doradus stars. For the southern objects, we gathered echelle spectra with the CORALIE ... [more ▼]

We report on observational results obtained for 78 objects originally classified as bona-fide or candidate gamma Doradus stars. For the southern objects, we gathered echelle spectra with the CORALIE spectrograph attached to the Euler telescope in 1998-2003 and/or Johnson-Cousins B,V,I_c observations with the MODULAR photometer attached to the 0.5-m SAAO telescope in 1999-2000. For the northern objects, we obtained Geneva U,B,B_1,B_2,V,V_1,G observations with the P7 photometer attached to the 1.2-m Mercator telescope in 2001-2004. At least 15 of our objects are binaries, of which 7 are new. For 6 binaries, we determined the orbit for the first time. At least 17 objects show profile variations and at least 12 objects are multiperiodic photometric variables. Our results allow us to upgrade 11 objects to bona-fide gamma Doradus stars and to downgrade 8 objects to constant up to the current detection limits. Mode identification is still ongoing, but so far, only l = 1 and 2 modes have been identified. [less ▲]

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See detailTime-dependent convection seismic study of delta Sct stars
Dupret, Marc-Antoine ULg; Grigahcène, A.; Garrido, R. et al

in Monthly Notices of the Royal Astronomical Society (2005), 361

We apply for the first time the time-dependent convection (TDC) treatment of Gabriel and Grigahcène et al. to the mode identification and seismic study of delta Sct stars. We consider the influence of ... [more ▼]

We apply for the first time the time-dependent convection (TDC) treatment of Gabriel and Grigahcène et al. to the mode identification and seismic study of delta Sct stars. We consider the influence of this treatment on the photometric amplitude ratios and phase differences, and compare our TDC results to frozen convection (FC) results. We also compare the results obtained with different values of the mixing-length (ML) parameter alpha. Finally, we identify the modes and perform a seismic study of the stars V784 Cassiopeae (Cas), 1 Monocerotis (Mon) and 28 Andromedae (And), and show that our TDC models agree better with observations than FC models. [less ▲]

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See detailTime-dependent convection seismic study of five gamma Doradus stars
Dupret, Marc-Antoine ULg; Grigahcène, A.; Garrido, R. et al

in Monthly Notices of the Royal Astronomical Society (2005), 360

We apply for the first time the time-dependent convection (TDC) treatment of Gabriel and Grigahcène et al. to the photometric mode identification in gamma Doradus (gamma Dor) stars. We consider the ... [more ▼]

We apply for the first time the time-dependent convection (TDC) treatment of Gabriel and Grigahcène et al. to the photometric mode identification in gamma Doradus (gamma Dor) stars. We consider the influence of this treatment on the theoretical amplitude ratios and phase differences. Comparison with the observed amplitudes and phases of the stars gamma Dor, 9 Aurigae, HD 207223 = HR 8330, HD 12901 and 48501 is presented and enables us to identify the degree l of the pulsation modes for four of them. We also determine the mode stability for different models of these stars. We show that our TDC models agree better with observations than with frozen convection models. Finally, we compare the results obtained with different values of the mixing-length parameter alpha. [less ▲]

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See detailA study of bright southern slowly pulsating B stars. III. Mode identification for singly-periodic targets in spectroscopy
De Cat, P.; Briquet, Maryline ULg; Daszynska-Daszkiewicz, J. et al

in Astronomy and Astrophysics (2005), 432

We present the results of the mode identification for a sample of 7 bright southern slowly pulsating B stars showing one pulsation frequency in the lambdalambda 413 nm Si II profiles. We combined the ... [more ▼]

We present the results of the mode identification for a sample of 7 bright southern slowly pulsating B stars showing one pulsation frequency in the lambdalambda 413 nm Si II profiles. We combined the results from (1) the method of photometric amplitudes; (2) the moment method; and (3) the amplitude and phase variation across the profile to search for the l and m values of the modes best fitting the data. It is the first time that the applicability of these techniques is tested to a sample of main-sequence g-mode pulsators. Combining the moment method with the amplitude and phase variations across the observed line profile gives an improvement in spectroscopic identification of low degree l g-mode pulsations. Using the variations of the higher order even moments < v[SUP]4[/SUP]> and < v[SUP]6[/SUP]> of the moment method solutions can also help. For HD 181558, HD 24587, HD 140873 and HD 177863, the photometric and spectroscopic results are compatible and point towards (l,m) = (1, +1) sectoral modes. For HD 215573, HD 53921 and HD 92287, the results are inconclusive. Our proposed methodology for mode identification is also applicable to gamma Doradus stars. Based on observations collected with the CAT Telescope of the European Southern Observatory and with the Swiss Photometric Telescope of the Geneva Observatory, both situated at La Silla in Chile. [less ▲]

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See detailAsteroseismology of the β Cephei star ν Eridani - III. Extended frequency analysis and mode identification
De Ridder, J.; Telting, J. H.; Balona, L. A. et al

in Monthly Notices of the Royal Astronomical Society (2004), 351

Using the large photometric and spectroscopic data sets of the ν Eridani multisite campaign given in our two recent papers (Aerts et al. and Handler et al.), we present an extended frequency analysis and ... [more ▼]

Using the large photometric and spectroscopic data sets of the ν Eridani multisite campaign given in our two recent papers (Aerts et al. and Handler et al.), we present an extended frequency analysis and a photometric mode identification. For the extended frequency analysis, we used an improved radial velocity time series, the second-moment time series and the line profiles themselves. In the radial velocity time series, we can now detect an additional pulsation frequency that was previously only found in photometric time series. We also report several new candidate pulsation frequencies. For seven frequencies, the photometric mode identification indicates that they belong to a radial mode and six dipole modes, and for three frequencies the degree l could not be unambiguously determined. We also placed ν Eri in the Hertzsprung-Russell diagram by determining T[SUB]eff[/SUB] using Geneva plus Strömgren photometric calibrations, spectral energy distribution fitting, by non-local thermodynamic equilibrium hydrogen, helium and silicon line profile fitting, and by determining log(L/L[SUB]solar[/SUB]) using the Hipparcos parallax and an Hβ calibration. [less ▲]

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See detailg-mode pulsations in slowly pulsating B stars
De Cat, P.; Daszynska-Daszkiewicz, J.; Briquet, Maryline ULg et al

in IAU Colloq. 193: Variable Stars in the Local Group (2004, May 01)

In this paper, we give an updated overview of the observed characteristics of g-mode pulsations in slowly pulsating B stars. These characteristics are based on the combined results of linear nonadiabatic ... [more ▼]

In this paper, we give an updated overview of the observed characteristics of g-mode pulsations in slowly pulsating B stars. These characteristics are based on the combined results of linear nonadiabatic analysis of the oscillations and a photometric and spectroscopic mode identification for a sample of 13 members. For 4 stars, at least one mode is stable in all the considered theoretical models. [less ▲]

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See detailLong-term multicolour photometry and high-resolution spectroscopy of the two gamma Doradus stars HD 12901 and HD 48501
Aerts, C.; Cuypers, J.; De Cat, P. et al

in Astronomy and Astrophysics (2004), 415

We gathered long-term multicolour Geneva UB[SUB]1[/SUB]BB[SUB]2[/SUB]V[SUB]1[/SUB]VG photometric and high-resolution (R=40 000) spectroscopic data of the two gamma Doradus stars HD 12901 and HD 48501. The ... [more ▼]

We gathered long-term multicolour Geneva UB[SUB]1[/SUB]BB[SUB]2[/SUB]V[SUB]1[/SUB]VG photometric and high-resolution (R=40 000) spectroscopic data of the two gamma Doradus stars HD 12901 and HD 48501. The photometry reveals three frequencies for each of the two stars: f[SUB]1[/SUB]=1.21563 c d[SUP]-1[/SUP], f[SUB]2[/SUB]=1.39594 c d[SUP]-1[/SUP] and f[SUB]3[/SUB]=2.18636 c d[SUP]-1[/SUP] for HD 12901 and f[SUB]1[/SUB]=1.09408 c d[SUP]-1[/SUP], f[SUB]2[/SUB]=1.29054 c d[SUP]-1[/SUP] and f[SUB]3[/SUB]=1.19924 c d[SUP]-1[/SUP] for HD 48501. The photometric amplitude is each time largest in the Geneva B[SUB]1[/SUB] filter and the variations in all the different filters are perfectly in phase within the measurement errors. Mode identification points out that the six modes are all l=1 modes and that the non-adiabatic temperature variations are extremely small, in contradiction to current theoretical predictions. Our spectra show that all the observed frequencies are intrinsic to the stars and cannot be due to binarity. We detect clear line-profile variations at low amplitude (<1 km s[SUP]-1[/SUP]) due to the oscillations of both targets. The estimated v sin i from the spectra are Ë 53 km s[SUP]-1[/SUP] for HD 12901 and Ë 29 km s[SUP]-1[/SUP] for HD 48501. It is at present unclear if the triplet-like structure for HD 48501 is the consequence of rotational splitting or of the large separation expected for high-order gravity modes in the asymptotic regime. Based on observations gathered with the Swiss 0.7 m telescope equipped with the photometer P 7 and with the Swiss 1.2 m Euler telescope equipped with the spectrograph CORALIE, both situated at La Silla, Chile. Reduced data available upon request from the first author. [less ▲]

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See detailA Hare and Hound in a BAG: Asteroseismology of Beta Cephei stars
Thoul, Anne ULg; Ausseloos, M.; Barban, C. et al

in Communications in Asteroseismology (2003), 143

Several members of the COROT Seismology Working Group (SWG) have performed several ``hare-and-hound'' exercises to prepare the data exploitation of the mission in the past few years. These exercises ... [more ▼]

Several members of the COROT Seismology Working Group (SWG) have performed several ``hare-and-hound'' exercises to prepare the data exploitation of the mission in the past few years. These exercises consist in reproducing a theoretical model on the basis of a light curve obtained from a frequency spectrum computed from an ``unknown'' theoretical model of a solar-like or a Delta Scuti star. Members of the BAG (Belgian Asteroseismology Group) have now shown that such an exercise in the mass range of Beta Cephei stars is extremely convincing, making these stars excellent targets for asteroseismology space missions. [less ▲]

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See detailSeismic modelling of the beta Cep star EN (16) Lacertae
Thoul, Anne ULg; Aerts, C.; Dupret, Marc-Antoine ULg et al

in Astronomy and Astrophysics (2003), 406(1), 287-292

We perform seismic modelling of the massive beta Cep star EN Lacertae. The starting point of our analysis is the spectroscopic mode identification recently performed. To this, we add a new updated ... [more ▼]

We perform seismic modelling of the massive beta Cep star EN Lacertae. The starting point of our analysis is the spectroscopic mode identification recently performed. To this, we add a new updated photometric mode identification based upon a non-adiabatic description of the eigenfunctions in the outer atmosphere. Both mode identifications agree and this allows us to fine-tune the stellar parameters of EN Lacertae with unprecedented precision. This is done by producing a huge amount of stellar models with different parameters and selecting those that fulfill the frequency values and the mode identification. Our study is the first one of its kind in which a reconcilation between observed pulsational characteristics and theoretical models can be achieved at a level that allows accurate determination of the basic stellar parameters of a massive oscillator. We derive a mass of M=9.62+/- 0.11 M[SUB]sun[/SUB] and an age of 15.7 million years if we assume that convective overshooting does not occur. [less ▲]

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See detailSpectroscopic mode identification for the beta Cephei star EN (16) Lacertae
Aerts, C.; Lehmann, H.; Briquet, Maryline ULg et al

in Astronomy and Astrophysics (2003), 399

We perform for the first time spectroscopic mode identification in the eclipsing binary beta Cephei star EN (16) Lac. This mode identification is based upon a time series of 942 line profiles of the He I ... [more ▼]

We perform for the first time spectroscopic mode identification in the eclipsing binary beta Cephei star EN (16) Lac. This mode identification is based upon a time series of 942 line profiles of the He I lambda lambda 6678 Åline in its spectrum. All three known frequencies f[SUB]1[/SUB], f,SUB>2,/SUB>, f[SUB]3[/SUB] of the star are present in the line-profile variations, but we failed to find additional modes. Using different identification methods we find conclusive evidence for the radial nature of the main mode and for the l=2, m=0 identification of the mode with frequency f[SUB]2[/SUB]. A unique identification of the third mode is not possible from the spectra, but we do derive that l[SUB]3[/SUB]<3. Fits to the amplitude and phase variability of the modes imply a rotation frequency between 0.1 and 0.4 c d[SUP]-1[/SUP]. The star's rotation axis is not aligned with the orbital axis. Based on observations gathered with the coudé spectrograph attached to the 2.0 m reflector telescope at Tautenburg Observatory. [less ▲]

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See detailA photometric mode identification method, including an improved non-adiabatic treatment of the atmosphere
Dupret, Marc-Antoine ULg; De Ridder, J.; De Cat, P. et al

in Astronomy and Astrophysics (2003), 398

We present an improved version of the method of photometric mode identification of Heynderickx et al. (\cite{hey}). Our new version is based on the inclusion of precise non-adiabatic eigenfunctions ... [more ▼]

We present an improved version of the method of photometric mode identification of Heynderickx et al. (\cite{hey}). Our new version is based on the inclusion of precise non-adiabatic eigenfunctions determined in the outer stellar atmosphere according to the formalism recently proposed by Dupret et al. (\cite{dup}). Our improved photometric mode identification technique is therefore no longer dependent on ad hoc parameters for the non-adiabatic effects. It contains the complete physical conditions of the outer atmosphere of the star, provided that rotation does not play a key role. We apply our method to the two slowly pulsating B stars HD 74560 and HD 138764 and to the beta Cephei star EN (16) Lac. Besides identifying the degree l of the pulsating stars, our method is also a tool for improving the knowledge of stellar interiors and atmospheres, by imposing constraints on parameters such as the metallicity and the mixing-length parameter alpha (a procedure we label non-adiabatic asteroseismology). The non-adiabatic eigenfunctions needed for the mode identification are available upon request from the authors. [less ▲]

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See detailMode Identification and Seismic Modelling of the Cep Star EN(16)Lac
Aerts, C.; Lehmann, H.; Scuflaire, Richard ULg et al

in Asteroseismology Across the HR Diagram (2003)

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See detailPhotometric Mode Identification in the Two Doradus Stars HD 12901 and HD 48501
Aerts, C.; Cuypers, J.; Dupret, Marc-Antoine ULg et al

in Asteroseismology Across the HR Diagram (2003)

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See detailAn Improved Method of Photometric Mode Identification: Applications to Slowly Pulsating B, beta Cephei, delta Scuti and gamma Doradus Stars
Dupret, Marc-Antoine ULg; Scuflaire, Richard ULg; Noels-Grötsch, Arlette ULg et al

in Astrophysics & Space Science (2003), 284

We present an improved version of the method of photometric mode identification based upon the inclusion of non-adiabatic eigenfunctions determined in the stellar atmosphere, according to the formalism ... [more ▼]

We present an improved version of the method of photometric mode identification based upon the inclusion of non-adiabatic eigenfunctions determined in the stellar atmosphere, according to the formalism recently proposed by Dupret et al. (2002). We apply our method to beta Cephei, Slowly Pulsating B, delta Scuti and gamma Doradus stars. Besides identifying the degree l of the pulsating stars, our method is also a tool for improving the knowledge of stellar interiors and atmospheres, by imposing constraints on the metallicity for beta Cephei and SPBs, the characteristics of the superficial convection zone for delta Scuti and gamma Doradus stars and the limb-darkening law. [less ▲]

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See detailInfluence of non-adiabatic temperature variations on line profile variations of slowly rotating beta Cep stars and SPBs. I. Non-adiabatic eigenfunctions in the atmosphere of a pulsating star
Dupret, Marc-Antoine ULg; De Ridder, J.; Neuforge, C. et al

in Astronomy and Astrophysics (2002), 385

In this study, we compute theoretical line profiles of a non-radially pulsating star, taking the non-adiabatic effects into account. These non-adiabatic effects are especially important in the atmosphere ... [more ▼]

In this study, we compute theoretical line profiles of a non-radially pulsating star, taking the non-adiabatic effects into account. These non-adiabatic effects are especially important in the atmosphere, where the spectral lines are formed, and must be accounted for. In this first paper of the series, we present a new treatment of the perturbed thermal and dynamical equations in the atmosphere of a pulsating star. We apply our formalism to the computation of non-adiabatic eigenfunctions in a typical beta Cephei star with low order p-modes and in a typical slowly pulsating B star with high-order g-modes. [less ▲]

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See detailInfluence of non-adiabatic temperature variations on line profile variations of slowly rotating beta Cephei stars and SPBs. II. Simulations of line profile time series
De Ridder, J.; Dupret, Marc-Antoine ULg; Neuforge, C. et al

in Astronomy and Astrophysics (2002), 385

We investigate to what extent non-adiabatic temperature variations at the surface of slowly rotating non-radially pulsating beta Cephei stars and slowly pulsating B stars affect silicon line profile ... [more ▼]

We investigate to what extent non-adiabatic temperature variations at the surface of slowly rotating non-radially pulsating beta Cephei stars and slowly pulsating B stars affect silicon line profile variations. We use the non-adiabatic amplitudes of the effective temperature and gravity variation presented in Dupret et al. (\cite{Dupret02}), together with a Kurucz intensity grid, to compute time series of line profile variations. Our simulations point out that the line shapes do not change significantly due to temperature variations. We find equivalent width variations of at most two percent of the mean equivalent width. We confront our results with observational equivalent width variations and with photometrically obtained effective temperature variations. Based on observations obtained with the Swiss photometric telescope and with the ESO/CAT telescope, at La Silla in Chile. [less ▲]

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