Asteroseismology of Massive Stars: Some Words of Caution Noels-Grötsch, Arlette ; ; Salmon, Sébastien et al in Meynet, Georges; Georgy, Cyril; Groh, Jose (Eds.) et al Proceedings of the International Astronomical Union S307 (2015, January 01) Although playing a key role in the understanding of the supernova phenomenon, the evolution of massive stars still suffers from uncertainties in their structure, even during their ``quiet'' main sequence ... [plus ▼] Although playing a key role in the understanding of the supernova phenomenon, the evolution of massive stars still suffers from uncertainties in their structure, even during their ``quiet'' main sequence phase and later on during their subgiant and helium burning phases. What is the extent of the mixed central region? In the local mixing length theory (LMLT) frame, are there structural differences using Schwarzschild or Ledoux convection criterion? Where are located the convective zone boundaries? Are there intermediate convection zones during MS and post-MS phase, and what is their extent and location? We discuss these points and show how asteroseismology could bring some light on these questions. [moins ▲] Visualisation de la référence détaillée: 27 (1 ULiège)Energetic effects in classical pulsators Dupret, Marc-Antoine ; ; et al in Proceedings of SOHO 18/GONG 2006/HELAS I, Beyond the spherical Sun (2006, October 01) Visualisation de la référence détaillée: 9 (1 ULiège)Theoretical damping rates and phase-lags for solar-like oscillations Dupret, Marc-Antoine ; ; et al in Proceedings of SOHO 18/GONG 2006/HELAS I, Beyond the spherical Sun (2006, October 01) Visualisation de la référence détaillée: 14 (2 ULiège)A non-local MLT treatment fitting 3D simulations Dupret, Marc-Antoine ; ; et al in Proceedings of SOHO 18/GONG 2006/HELAS I, Beyond the spherical Sun (2006, October 01) Visualisation de la référence détaillée: 12 (1 ULiège)Instability strip for pre-main-sequence stars ; Dupret, Marc-Antoine ; 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 ... [plus ▼] 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. [moins ▲] Visualisation de la référence détaillée: 13 (0 ULiège)Non-local time-dependent treatments of convection in A-G type stars Dupret, Marc-Antoine ; ; 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 ... [plus ▼] 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. [moins ▲] Visualisation de la référence détaillée: 23 (1 ULiège)Convection-pulsation interaction: theories and applications Dupret, Marc-Antoine ; ; Gabriel, Maurice 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 ... [plus ▼] 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. [moins ▲] Visualisation de la référence détaillée: 14 (0 ULiège)Theoretical Aspects of g-mode Pulsations in gamma Doradus Stars Dupret, Marc-Antoine ; ; 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 ... [plus ▼] 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. [moins ▲] Visualisation de la référence détaillée: 38 (2 ULiège)Application of time-dependent convection models to the photometric mode identification in gamma Doradus stars Dupret, Marc-Antoine ; ; 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 ... [plus ▼] 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. [moins ▲] Visualisation de la référence détaillée: 20 (3 ULiège)Influence of overshooting and metallicity on the delta Scuti and gamma Doradus instability strips ; Dupret, Marc-Antoine ; 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 ... [plus ▼] 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. [moins ▲] Visualisation de la référence détaillée: 31 (2 ULiège)Application of time-dependent convection models to the photometric mode identification in delta Scuti stars Dupret, Marc-Antoine ; ; et al 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 ... [plus ▼] 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. [moins ▲] Visualisation de la référence détaillée: 16 (2 ULiège)Time-dependent convection seismic study of delta Sct stars Dupret, Marc-Antoine ; ; 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 ... [plus ▼] 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. [moins ▲] Visualisation de la référence détaillée: 25 (3 ULiège)Time-dependent convection seismic study of five gamma Doradus stars Dupret, Marc-Antoine ; ; 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 ... [plus ▼] 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. [moins ▲] Visualisation de la référence détaillée: 11 (1 ULiège)Convection-pulsation coupling. II. Excitation and stabilization mechanisms in delta Sct and gamma Dor stars Dupret, Marc-Antoine ; ; et al in Astronomy and Astrophysics (2005), 435 We apply here the Time Dependent Convection (TDC) treatment presented in our earlier paper in this series to the study of delta Sct and gamma Dor pulsating stars. Stabilization of the delta Sct p-modes at ... [plus ▼] We apply here the Time Dependent Convection (TDC) treatment presented in our earlier paper in this series to the study of delta Sct and gamma Dor pulsating stars. Stabilization of the delta Sct p-modes at the red edge of the Instability Strip (IS) and the driving of the gamma Dor g-modes are explained by our models. Theoretical IS obtained with different values of the Mixing Length (ML) parameter alpha are compared to observations and a good agreement is obtained for alpha between 1.8 and 2. The influence of each term of our TDC treatment (perturbation of convective flux, turbulent pressure, and turbulent kinetic energy dissipation) on the eigenfrequencies and on the driving and damping mechanisms is investigated. Finally, we show that our TDC models predict the likely existence of hybrid stars with both delta Sct p-modes and gamma Dor g-modes oscillations. [moins ▲] Visualisation de la référence détaillée: 13 (1 ULiège)Convection-pulsation coupling. I. A mixing-length perturbative theory ; Dupret, Marc-Antoine ; Gabriel, Maurice et al in Astronomy and Astrophysics (2005), 434 We present in details a time-dependent convection treatment in the frame of the Mixing-Length Theory (MLT). Following the original ideas by Unno (1967, PASJ, 19, 140), this theory has been developed by ... [plus ▼] We present in details a time-dependent convection treatment in the frame of the Mixing-Length Theory (MLT). Following the original ideas by Unno (1967, PASJ, 19, 140), this theory has been developed by Gabriel et al. (1974, Bull. Ac. Roy. Belgique, Classe des Sciences, 60, 866) and Gabriel (1996, Bull. Astron. Soc. India, 24, 233). In this paper, we present it in a united form, we detail the basic derivations and approximations and give final improvements. A new perturbation of the energy closure equation is proposed for the first time, making it possible to avoid the occurrence of short wavelength spatial oscillations of the thermal eigenfunctions. This theory accounts for the perturbation of the convective flux, the turbulent Reynolds stress and the turbulent kinetic energy dissipation. It has been numerically implemented in a non-radial non-adiabatic pulsation code and the first results published in a Letter by Dupret et al. (2004a, A&A, 414, L17) indicate that the theory predicts the observed red border of the lower end of the instability strip and the driving mechanism of the recently discovered gamma Dor stars. [moins ▲] Visualisation de la référence détaillée: 48 (2 ULiège)Convection-Oscillations Interaction in F-G Type Main Sequence Stars Dupret, Marc-Antoine ; ; et al in SOHO 14 Helio- and Asteroseismology: Towards a Golden Future (2004, October 01) Visualisation de la référence détaillée: 12 (4 ULiège)Theoretical Instability Strips and Non-Adiabatic Photometric Observables for d Scut and g DOR Stars Dupret, Marc-Antoine ; ; et al in SOHO 14 Helio- and Asteroseismology: Towards a Golden Future (2004, October 01) Visualisation de la référence détaillée: 10 (2 ULiège)Influence of the convective flux perturbation on stellar oscillations: application to Delta Scuti and Gamma Doradus stars ; Dupret, Marc-Antoine ; et al in Communications in Asteroseismology (2004), 145 We present a theory of convection-oscillation interaction. In our nonradial nonadiabatic pulsation code, the variation of the convective flux (radial and transversal components) is taken into account ... [plus ▼] We present a theory of convection-oscillation interaction. In our nonradial nonadiabatic pulsation code, the variation of the convective flux (radial and transversal components) is taken into account, following the theory of M. Gabriel, within the mixing length approach. We explore the influence of the convective flux variation on mode stability near the red-edge of the Delta Scuti instability strip and the excitation mechanisms of Gamma Doradus stars. [moins ▲] Visualisation de la référence détaillée: 14 (0 ULiège)Non-adiabatic seismic study of the thin convective envelope of delta Scuti stars Dupret, Marc-Antoine ; ; et al in IAU Colloq. 193: Variable Stars in the Local Group (2004, May 01) For delta Sct stars, the theoretical predictions of a non-adiabatic pulsation code are very dependent on the characteristics of the thin convective envelope of the models (Balona and Evers 1999). The ... [plus ▼] For delta Sct stars, the theoretical predictions of a non-adiabatic pulsation code are very dependent on the characteristics of the thin convective envelope of the models (Balona and Evers 1999). The treatment of the non-adiabatic interaction between convection and pulsation also has a significant impact on the results, particularly near the red edge of the instability strip. The non-adiabatic theoretical predictions can be tested upon observations by comparing them to the amplitude ratios and phase differences as observed in different color passbands (Dupret et al. 2003). In the first part of this paper, we compare the results obtained by adopting different treatments of convection in the interior and atmosphere models: mixing-length theory (MLT) and full spectrum of turbulence (FST) (Canuto et al. 1996, CGM). In the second part, we examine the problem of the interaction between convection and pulsation and compare the mode stability obtained with and without including time-dependent convection in our non-adiabatic code. [moins ▲] Visualisation de la référence détaillée: 24 (1 ULiège)Theoretical instability strips for delta Scuti and gamma Doradus stars Dupret, Marc-Antoine ; ; et al in Astronomy and Astrophysics (2004), 414 New theoretical instability strips for delta Sct and gamma Dor stars are presented. These results have been obtained taking into account the perturbation of the convective flux following the treatment of ... [plus ▼] New theoretical instability strips for delta Sct and gamma Dor stars are presented. These results have been obtained taking into account the perturbation of the convective flux following the treatment of Gabriel (\cite{Gabriel1996}). For the first time, the red edge of the delta Sct instability strip for non-radial modes is obtained. The influence of this time-dependent convection (TDC) on the driving of the gamma Dor gravity modes is investigated. The results obtained for different values of the mixing-length parameter alpha are compared for the gamma Dor models. A good agreement with observations is found for models with alpha between 1.8 and 2.0. [moins ▲] Visualisation de la référence détaillée: 42 (2 ULiège) |
||