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Energetic study of solar-like oscillations in red giants Grosjean, Mathieu Doctoral thesis (2015) Observations of solar-like oscillations by CoRoT and Kepler space-borne telescopes, have opened new opportunities for the energetic modelling of these oscillations. In particular, oscillations propagating ... [more ▼] Observations of solar-like oscillations by CoRoT and Kepler space-borne telescopes, have opened new opportunities for the energetic modelling of these oscillations. In particular, oscillations propagating in both the convective envelope and the radiative core of evolved low-mass stars, called mixed-modes, have been detected, allowing us to investigate various physical processes acting on oscillations in these two regions. Theoretical predictions for the linewidths and the amplitudes of solar-like oscillations, as obtained and discussed in this thesis, strongly depend on the treatment of the interaction between convection and oscillations. Observed properties of solar-like oscillations thus gives us the opportunity to test and constrain this treatment. The comparisons between observed and theoretical linewidths of main-sequence stars allow us to constrain the parameters of the time-dependent treatment of convection and to produce more accurate results. The remaining discrepancies will give us new clues for the improvement of the treatment of the interaction between convection and oscillations. The modelling of the energetic aspects of solar-like oscillations in red giants allows us to derive a detectability limit for mixed-modes. These results are in overall good agreement with typical red-giant observed power spectra. A detailed comparison between an observed subgiant and the corresponding theoretical predic- tions confirms that the main aspects of the observed energetic properties of solar-like oscillations are well reproduced by the theoretical modelling. Discrepancies between observed and theoret- ical linewidths of quadrupole mixed-modes lead us to invoke the existence of a new damping mechanism in the core of this star. [less ▲] Detailed reference viewed: 43 (6 ULg)Non-adiabatic study of the Kepler subgiant KIC 6442183 Grosjean, Mathieu ; Dupret, Marc-Antoine ; et al in The Space Photometry Revolution CoRoT Symposium 3, Kepler KASC-7 joint meeting (2015, September) Thanks to the precision of Kepler observations, [3] were able to measure the linewidth and amplitude of individual modes (including mixed modes) in several sub- giant power spectra. We perform a forward ... [more ▼] Thanks to the precision of Kepler observations, [3] were able to measure the linewidth and amplitude of individual modes (including mixed modes) in several sub- giant power spectra. We perform a forward modelling of a Kepler subgiant based on sur- face properties and observed frequencies. Non-adiabatic computations including a time- dependent treatment of convection give the lifetimes of radial and non-radial modes. Next, combining the lifetimes and inertias with a stochastic excitation model gives the ampli- tudes of the modes. We can now directly compare theoretical and observed linewidths and amplitudes of mixed-modes to obtain new constraints on our theoretical models. [less ▲] Detailed reference viewed: 23 (6 ULg)Theoretical power spectra of mixed modes in low-mass red giant stars Grosjean, Mathieu ; Dupret, Marc-Antoine ; et al in Astronomy and Astrophysics (2014), 572 CoRoT and Kepler observations of red giant stars revealed very rich spectra of non-radial solar-like oscillations. Of particular interest was the detection of mixed modes that exhibit significant ... [more ▼] CoRoT and Kepler observations of red giant stars revealed very rich spectra of non-radial solar-like oscillations. Of particular interest was the detection of mixed modes that exhibit significant amplitude, both in the core and at the surface of the stars. It opens the possibility of probing the internal structure from their innermost layers up to their surface throughout their evolution on the red giant branch, as well as on the red clump. Our objective is primarily to provide physical insight into the mechanism responsible for mixed-mode amplitudes and lifetimes. Subsequently, we aim at understanding the evolution and structure of red-giant spectra along with their evolution. The study of energetic aspects of these oscillations is also important for predicting the mode parameters in the power spectrum. Non-adiabatic computations, including a time-dependent treatment of convection, are performed and provide the lifetimes of radial and non-radial mixed modes. We then combine these mode lifetimes and inertias with a stochastic excitation model that gives us their heights in the power spectra. For stars representative of CoRoT and Kepler observations, we show under which circumstances mixed modes have heights comparable to radial ones. We stress the importance of the radiative damping in determining the height of mixed modes. Finally, we derive an estimate for the height ratio between a g-type and a p-type mode. This can thus be used as a first estimate of the detectability of mixed modes. [less ▲] Detailed reference viewed: 31 (5 ULg)Theoretical power spectra of solar-like oscillations in evolved low-mass stars. Grosjean, Mathieu ; Dupret, Marc-Antoine Scientific conference (2014) Detailed reference viewed: 8 (1 ULg)Non-adiabatic study of the Kepler subgiant KIC 6442183 Grosjean, Mathieu ; Dupret, Marc-Antoine ; et al Poster (2014) Detailed reference viewed: 13 (1 ULg)Energetical aspects of solar-like oscillations in red giants Grosjean, Mathieu ; Dupret, Marc-Antoine ; et al in Precision Asteroseismology, Proceedings of the International Astronomical Union, IAU Symposium, Volume 301 (2014) Detailed reference viewed: 16 (1 ULg)Energetical aspects of solar-like oscillations in red giants Grosjean, Mathieu ; Dupret, Marc-Antoine ; et al Conference (2013, December) CoRoT and Kepler observations of red giants reveal very rich spectra of non-radial solar- like oscillations allowing us to probe their internal structure. The study of energetic aspects of these ... [more ▼] CoRoT and Kepler observations of red giants reveal very rich spectra of non-radial solar- like oscillations allowing us to probe their internal structure. The study of energetic aspects of these oscillations is of great importance to predict the peak parameters in the power spectrum. The theoretical determination of lifetimes (or equivalently width) of the modes require non- adiabatic computations. Next, combined with a stochastic excitation model, we can also predict the height of the mode and finally obtain theoretical power spectra. Comparison between our theoretical predictions with observations give important constraint on red-giants models. Lifetimes and amplitudes of modes trapped in the envelope (e.g. radial modes) constrain the characteristics of the convective envelope and its time-dependent interaction with oscillations. Lifetimes of mixed-modes (mainly dipolar modes) strongly depend on mode trapping, allowing us to probe the core of red-giants. I will discuss under which circumstances mixed modes are detectable for a large variety of red-giant stellar models, with emphasis on the effect of the evolutionary status of the star (along the red-giant branch and during the He-burning phase) for a wide range of stellar masses (from 0.7 to 4 Msun ) on theoretical power spectra. [less ▲] Detailed reference viewed: 8 (0 ULg)Evolution of the theoretical power spectrum of solar-like oscillations along the ascending phase on the red giant branch. Grosjean, Mathieu ; Dupret, Marc-Antoine ; et al in Astronomical Society of the Pacific Conference Series (2013, December), 479 CoRoT and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. An important question comes from the observation of mixed ... [more ▼] CoRoT and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. An important question comes from the observation of mixed modes : When during the star’s ascension on the RGB are mixed-modes more likely to be detectable ? We follow the evolution of a star on the RGB and investigate the eﬀect of its ascension on theoretical power spectrum. Equilibrium models (computed with the code ATON) represent four diﬀerent stages of a star on the RGB. The mass of the star (1.5M") is in the typical mass range of stars observed by CoRoT and Kepler. We used a non-radial non-adiabatic code to compute the theoretical solar-like oscillations of these models. An important output of these calculations is the theoretical lifetimes of the modes. Then we computed the oscillation amplitudes through a stochastic excitation model. These computations allow us to draw theoretical power spectrum and discuss the possibility to observe mixed-modes at diﬀerent evolutionary stages on the RGB. We found that structure modiﬁcations in a star ascending the RGB have an important impact on theoretical power spectrum of solar-like oscillations. Eﬃciencies of trapping and lifetimes of mixed modes are indeed strongly aﬀected by this evolution. [less ▲] Detailed reference viewed: 20 (2 ULg)Energetical aspects of solar-like oscillations in red giants Grosjean, Mathieu ; Dupret, Marc-Antoine Conference (2013, August 23) CoRoT and Kepler observations of red giants reveal a large variety of spectra of non- radial solar- like oscillations. Up to now we understood pretty well the frequency patterns for the different global ... [more ▼] CoRoT and Kepler observations of red giants reveal a large variety of spectra of non- radial solar- like oscillations. Up to now we understood pretty well the frequency patterns for the different global properties or different evolutionary stages of the stars. Here we are interested in the theoretical predictions for the two other components of a power spectra (the linewitdths and the heights). The study of energetic aspects of these oscillations is of great importance to predict the peak parameters in the power spectrum. I will discuss under which circumstances mixed modes are detectable for a large variety of red-giant stellar models, with emphasis on the effect of the evolutionary status of the star along the red-giant branch, for a wide range of stellar masses (from 1 to 2M⊙ ) on theoretical power spectra. [less ▲] Detailed reference viewed: 32 (6 ULg)Non-radial, non-adiabatic solar-like oscillations in RGB and HB stars Grosjean, Mathieu ; Dupret, Marc-Antoine ; et al in EPJ Web of Conferences (2013, March 01), 43 CoRoT and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. We compare the theoretical spectrum of two red giants in ... [more ▼] CoRoT and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. We compare the theoretical spectrum of two red giants in the same region of the HR diagram but in different evolutionary phases. We present here our first results on the inertia, lifetimes and amplitudes of the oscillations and discuss the differences between the two stars. [less ▲] Detailed reference viewed: 21 (9 ULg)Evolution of the theoretical power spectrum of solar-like oscillations along the ascending phase on the red giant branch. Grosjean, Mathieu ; Montalban Iglesias, Josefa ; et al Poster (2012, November) CoRoT and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. An important question comes from the observation of mixed ... [more ▼] CoRoT and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. An important question comes from the observation of mixed modes : When during the star’s ascension on the RGB are mixed-modes more likely to be detectable ? We follow the evolution of a star on the RGB and investigate the eﬀect of its ascension on theoretical power spectrum. Equilibrium models (computed with the code ATON) represent four diﬀerent stages of a star on the RGB. The mass of the star (1.5M") is in the typical mass range of stars observed by CoRoT and Kepler. We used a non-radial non-adiabatic code to compute the theoretical solar-like oscillations of these models. An important output of these calculations is the theoretical lifetimes of the modes. Then we computed the oscillation amplitudes through a stochastic excitation model. These computations allow us to draw theoretical power spectrum and discuss the possibility to observe mixed-modes at diﬀerent evolutionary stages on the RGB. We found that structure modiﬁcations in a star ascending the RGB have an important impact on theoretical power spectrum of solar-like oscillations. Eﬃciencies of trapping and lifetimes of mixed modes are indeed strongly aﬀected by this evolution. [less ▲] Detailed reference viewed: 13 (2 ULg)Non-radial, non-adiabatic solar-like oscillations in RGB and HB stars Grosjean, Mathieu ; Dupret, Marc-Antoine ; et al Poster (2012, July) Corot and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. We compare the theoretical spectrum (amplitudes and life ... [more ▼] Corot and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. We compare the theoretical spectrum (amplitudes and life- times) of two red giants in the same region of the HR diagram but in different evolutionary phases. The lifetimes are obtained by computing theoretical non-adiabatic non-radial solar-like oscillations for mixed modes in the two models. Thanks to this, we have been able to compute the oscillation amplitudes through a stochastic excitation model. We present here our first results on the inertia, damping rates and amplitudes of the oscillations in the two stars and discuss the trapping, the visibilities and the am- plitudes of the different modes. The differences in the spectra of the two stars are also investigated. As already known, the period spacings in the two models are very different. Moreover, we find significant differences in amplitudes and lifetimes between the two models. [less ▲] Detailed reference viewed: 40 (7 ULg)Non-radial non-adiabatic solar like oscillations in red giants : Evolutionnary effects on theoretical power spectrum. Grosjean, Mathieu ; Dupret, Marc-Antoine Scientific conference (2012) Corot and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. The study of non-adiabatic and energetic aspects of these ... [more ▼] Corot and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. The study of non-adiabatic and energetic aspects of these oscillations is of great importance to predict not only the frequencies but also the FWMH and Heights of the peaks in power spectrum. This two observables are indeed directly related to modes lifetimes, necessitating a non-adiabatic approach. The height also depends on the energy injected in the mode by the turbulence in the upper convective-zone. We use a stochastic excitation model to compute the amplitudes of each modes. We investigate the differences in power spectrum between an RGB and an HB stars with the same global parameters. We also follow the evolution of a star on the RGB and investigate the effect of its ascension on theoretical power spectrum to predict when on the RGB are mixed-modes more likely to be detectable. [less ▲] Detailed reference viewed: 4 (1 ULg) |
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