Seismic diagnostics for transport of angular momentum in stars

Marques, J. P.; Goupil, M. J.; Lebreton, Y.; Talon, Suzanne; Palacios, Ana; Belkacem, K.; Ouazzani, R. M.; Mosser, B.; Moya, A.; Morel, Pierre; Pichon, B.; Mathis, S.; Zahn, Jean-Paul; Turck‐Chièze, S.; Nghiem, P.

doi:10.1051/0004-6361/201220211

Cited by 285 publications

(289 citation statements)

References 90 publications

(146 reference statements)

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“…This was qualitatively expected, considering that the deepest layers below the H-burning shell contract, while the layers above expand. However, the core rotation rates measured with seismology are several orders of magnitude below the values predicted by theoretical models that include rotationinduced transport of angular momentum (Eggenberger et al 2012;Marques et al 2013). On the red giant branch (RGB), seismic measurements of the core rotation for several hundreds of Kepler targets led to the striking observation that the core of red giants in fact spins down (Mosser et al 2012), which is also at odds with current theoretical models.…”

Section: Introductionmentioning

confidence: 82%

Near-degeneracy effects on the frequencies of rotationally-split mixed modes in red giants

Deheuvels

Ouazzani

Basu

2017

A&A

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Context. The Kepler space mission has made it possible to measure the rotational splittings of mixed modes in red giants, thereby providing an unprecedented opportunity to probe the internal rotation of these stars. Aims. Asymmetries have been detected in the rotational multiplets of several red giants. This is unexpected since all the red giants whose rotation profiles have been measured thus far are found to rotate slowly, and low rotation, in principle, produces symmetrical multiplets. Our aim here is to explain these asymmetries and find a way of exploiting them to probe the internal rotation of red giants. Methods. We show that in the cases where asymmetrical multiplets were detected, near-degeneracy effects are expected to occur, because of the combined effects of rotation and mode mixing. Such effects have not been taken into account so far. By using both perturbative and non-perturbative approaches, we show that near-degeneracy effects produce multiplet asymmetries that are very similar to the observations. We then propose and validate a method based on the perturbative approach to probe the internal rotation of red giants using multiplet asymmetries. Results. We successfully apply our method to the asymmetrical l = 2 multiplets of the Kepler young red giant KIC 7341231 and obtain precise estimates of its mean rotation in the core and the envelope. The observed asymmetries are reproduced with a good statistical agreement, which confirms that near-degeneracy effects are very likely the cause of the detected multiplet asymmetries. Conclusions. We expect near-degeneracy effects to be important for l = 2 mixed modes all along the red giant branch (RGB). For l = 1 modes, these effects can be neglected only at the base of the RGB. They must therefore be taken into account when interpreting rotational splittings and as shown here, they can bring valuable information about the internal rotation of red giants.

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Section: Introductionmentioning

confidence: 82%

Near-degeneracy effects on the frequencies of rotationally-split mixed modes in red giants

Deheuvels

Ouazzani

Basu

2017

A&A

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“…We have modelled the star with the stellar evolution code Cesam2k (Morel & Lebreton 2008;Marques et al 2013). Following Lebreton et al (2008), to ensure numerical accuracy, the models were calculated with ≈2000 mesh points and ≈100 time steps were taken to reach the optimized final model of the star.…”

Section: Model Input Physics and Chemical Compositionmentioning

confidence: 99%

“…In that case, additional free coefficients enter the modelling: a coefficient K w intervenes in the treatment of magnetic braking by stellar winds (see Eq. (9) in Marques et al 2013), following the relation by Kawaler (1988). We adjusted K w so that the final model has the observed rotation period.…”

Section: Model Input Physics and Chemical Compositionmentioning

confidence: 99%

Asteroseismology for “à la carte” stellar age-dating and weighing

Lebreton

Goupil

2014

A&A

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157

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Context. In the context of the space missions CoRoT, Kepler, Gaia, TESS, and PLATO, precise and accurate stellar ages, masses, and radii are of paramount importance. For instance, they are crucial for constraining scenarii of planetary formation and evolution. Aims. We aim at quantifying how detailed stellar modelling can improve the accuracy and precision on age and mass of individual stars. To that end, we adopt a multifaceted approach where we carefully examine how the number of observational constraints as well as the uncertainties on observations and on model input physics affect the results of age-dating and weighing. Methods. We modelled in detail the exoplanet host-star HD 52265, a main-sequence, solar-like oscillator that CoRoT observed for four months. We considered different sets of observational constraints (Hertzsprung-Russell data, metallicity, various sets of seismic constraints). For each case, we determined the age, mass, and properties of HD 52265 inferred from stellar models, and we quantified the impact of the model input physics and free parameters. We also compared model ages with ages derived by empirical methods or Hertzsprung-Russell diagram inversion. Results. For our case study HD 52265, our seismic analysis provides an age A = 2.10−2.54 Gyr, a mass M = 1.14−1.32 M , and a radius R = 1.30−1.34 R , which corresponds to age, mass, and radius uncertainties of ∼10, ∼7, and ∼1.5 per cent, respectively. These uncertainties account for observational errors and current state-of-the-art stellar model uncertainties. Our seismic study also provides constraints on surface convection properties through the mixing-length, which we find to be 12−15 per cent lower than the solar value. On the other hand, because of helium-mass degeneracy, the initial helium abundance is determined modulo the mass value. Finally, we evaluate the seismic mass of the exoplanet to be M p sin i = 1.17−1.26 M Jupiter , much more precise than what can be derived by Hertzsprung-Russell diagram inversion. Conclusions. We demonstrate that asteroseismology allows us to substantially improve the age accuracy that can be achieved with other methods. We emphasize that the knowledge of the mean properties of stellar oscillations -such as the large frequency separation -is not enough to derive accurate ages. We need precise individual frequencies to narrow the age scatter that is a result of the model input physics uncertainties. Further progress is required to better constrain the physics at work in stars and the stars helium content. Our results emphasize the importance of precise classical stellar parameters and oscillation frequencies such as will be obtained by the Gaia and PLATO missions.

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“…The stellar model is computed with the CESTAM code (Code d'Évolution Stellaire, avec Transport, Adaptatif et Modulaire, Marques et al 2013). Transport of angular momentum induced by rotation according to Zahn (1992) is included.…”

Section: Theoretical Frequency Spectra For Red Giantsmentioning

confidence: 99%

Non-perturbative effect of rotation on dipolar mixed modes in red giant stars

Ouazzani

Goupil

Dupret

et al. 2013

A&A

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Context. The space missions CoRoT and Kepler provide high-quality data that allow us to test the transport of angular momentum in stars by the seismic determination of the internal rotation profile. Aims. Our aim is to test the validity of seismic diagnostics for red giant rotation that are based on a perturbative method and to investigate the oscillation spectra when the validity does not hold. Methods. We use a non-perturbative approach implemented in the ACOR code that accounts for the effect of rotation on pulsations and solves the pulsation eigenproblem directly for dipolar oscillation modes. Results. We find that the limit of the perturbation to first order can be expressed in terms of the rotational splitting compared to the frequency separation between consecutive dipolar modes. Above this limit, non-perturbative computations are necessary, but only one term in the spectral expansion of modes is sufficient as long as the core rotation rate remains significantly smaller than the pulsation frequencies. Each family of modes with different azimuthal symmetry, m, has to be considered separately. In particular, in case of rapid core rotation, the density of the spectrum differs significantly from one m-family of modes to another, so that the differences between the period spacings associated with each m-family can constitute a promising guideline toward a proper seismic diagnostic for rotation.

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Seismic diagnostics for transport of angular momentum in stars

Cited by 285 publications

References 90 publications

Near-degeneracy effects on the frequencies of rotationally-split mixed modes in red giants

Near-degeneracy effects on the frequencies of rotationally-split mixed modes in red giants

Asteroseismology for “à la carte” stellar age-dating and weighing

Non-perturbative effect of rotation on dipolar mixed modes in red giant stars

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