Pulsations of rapidly rotating stars with compositional discontinuities

Reese, D. R.; Lara, F. Espinosa; Rieutord, M.

doi:10.1017/s1743921313014270

Cited by 2 publications

(1 citation statement)

References 11 publications

(18 reference statements)

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“…The amplitudes of eigenfunctions at each side of the discontinuities strongly change from one mode to another. Therefore, we have adjusted the oscillation code to ensure the continuity of the Lagrangian perturbations of pressure, gravitational potential, and its gradient (see also Reese et al 2014). Special care was also given to the computation of the BruntVäisälä frequency as it significantly affects our results.…”

Section: Non-adiabatic Computationsmentioning

confidence: 99%

Theoretical power spectra of mixed modes in low-mass red giant stars

Grosjean

Dupret

Belkacem

et al. 2014

A&A

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Context. 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 inner-most layers up to their surface along their evolution on the red giant branch as well as on the red-clump. Aims. Our objective is primarily to provide physical insight into the physical mechanism responsible for mixed-modes amplitudes and lifetimes. Subsequently, we aim at understanding the evolution and structure of red giants spectra along with their evolution. The study of energetic aspects of these oscillations is also of great importance to predict the mode parameters in the power spectrum. Methods. 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. Results. 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 the determination of 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.

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Section: Non-adiabatic Computationsmentioning

confidence: 99%

Theoretical power spectra of mixed modes in low-mass red giant stars

Grosjean

Dupret

Belkacem

et al. 2014

A&A

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Oscillations of 2D ESTER models

Reese

Mirouh

Lara

et al. 2021

A&A

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Context. Recent numerical and theoretical considerations have shown that low-degree acoustic modes in rapidly rotating stars follow an asymptotic formula. In parallel, recent studies have revealed the presence of regular pulsation frequency patterns in rapidly rotating δ Scuti stars that seem to match theoretical expectations. Aims. In this context, a key question is whether strong gradients or discontinuities can adversely affect the asymptotic frequency pattern to the point of hindering its identification. Other important questions are how rotational splittings are affected by the 2D rotation profiles expected from baroclinic effects and whether it is possible to probe the rotation profile using these splittings. Methods. In order to address these questions, we numerically calculate stellar pulsation modes in continuous and discontinuous rapidly rotating models produced by the 2D Evolution STEllaire en Rotation (ESTER) code. This code self-consistently calculates the rotation profile based on baroclinic effects and uses a spectral multi-domain approach, thus making it possible to introduce discontinuities at the domain interfaces without loss of numerical accuracy. The pulsation calculations are carried out using an adiabatic version of the Two-dimensional Oscillation Program (TOP) code. The variational principle is then used to confirm the high numerical accuracy of the pulsation frequencies and to derive an integral formula for the generalised rotational splittings. Acoustic glitch theory, combined with ray dynamics, is applied to the discontinuous models in order to interpret their pulsation spectra. Results. Our results show that the generalised rotational splittings are very well approximated by the integral formula, except for modes involved in avoided crossings. This potentially allows the application of inverse theory for probing the rotation profile. We also show that glitch theory applied along the island mode orbit can correctly predict the periodicity of the glitch frequency pattern produced by the discontinuity or Γ1 dip related to the He II ionisation zone in some of the models. Furthermore, the asymptotic frequency pattern remains sufficiently well preserved to potentially allow its detection in observed stars.

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Pulsations of rapidly rotating stars with compositional discontinuities

Cited by 2 publications

References 11 publications

Theoretical power spectra of mixed modes in low-mass red giant stars

Theoretical power spectra of mixed modes in low-mass red giant stars

Oscillations of 2D ESTER models

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