References of "Grosjean, Mathieu"
     in
Bookmark and Share    
Full Text
See detailNon-adiabatic study of the Kepler subgiant KIC 6442183
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg; Belkacem, Kevin et al

in The Space Photometry Revolution CoRoT Symposium 3, Kepler KASC-7 joint meeting (in press)

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: 4 (1 ULg)
Full Text
Peer Reviewed
See detailTheoretical power spectra of mixed modes in low-mass red giant stars
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg; Belkacem, Kevin 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: 9 (4 ULg)
Full Text
See detailNon-adiabatic study of the Kepler subgiant KIC 6442183
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg; Belkacem, Kevin et al

Poster (2014)

Detailed reference viewed: 8 (1 ULg)
Full Text
See detailEnergetical aspects of solar-like oscillations in red giants
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg; Belkacem, Kevin et al

in Precision Asteroseismology, Proceedings of the International Astronomical Union, IAU Symposium, Volume 301 (2014)

Detailed reference viewed: 13 (1 ULg)
Full Text
See detailEnergetical aspects of solar-like oscillations in red giants
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg; Belkacem, Kevin 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: 2 (0 ULg)
Full Text
See detailEvolution of the theoretical power spectrum of solar-like oscillations along the ascending phase on the red giant branch.
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg; Belkacem, Kevin 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: 17 (2 ULg)
Full Text
See detailEnergetical aspects of solar-like oscillations in red giants
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg

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: 23 (6 ULg)
Full Text
See detailNon-radial, non-adiabatic solar-like oscillations in RGB and HB stars
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg; Belkacem, K. 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: 18 (9 ULg)
Full Text
See detailEvolution of the theoretical power spectrum of solar-like oscillations along the ascending phase on the red giant branch.
Grosjean, Mathieu ULg; Montalban Iglesias, Josefa ULg; Samadi, Reza 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: 10 (2 ULg)
Full Text
See detailNon-radial, non-adiabatic solar-like oscillations in RGB and HB stars
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg; Belkacem, Kevin 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: 28 (7 ULg)
See detailNon-radial non-adiabatic solar like oscillations in red giants : Evolutionnary effects on theoretical power spectrum.
Grosjean, Mathieu ULg; Dupret, Marc-Antoine ULg

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 (0 ULg)