Seismic diagnostics for transport of angular momentum in stars

Goupil, M. J.; Mosser, B.; Marques, J. P.; Ouazzani, R. M.; Belkacem, K.; Lebreton, Y.; Samadi, R.

doi:10.1051/0004-6361/201220266

Cited by 114 publications

(194 citation statements)

References 31 publications

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“…However, in the latter case, a large number of l = 1 modes can be detected, and these have a wide variety of natures ranging from g-dominated to p-dominated. Deheuvels et al (2012) showed that all the nonrotating models that provide satisfactory matches to the frequencies of the m = 0 components of the observed l = 1 modes predict a similar trapping of the dipolar modes, quantified by the parameter ζ defined as the ratio between the mode inertia in the g-mode cavity and the total mode inertia, that is, Goupil et al (2013) showed that the trapping of l = 1 modes can even be estimated reliably from the mode frequencies themselves, independently of stellar models, using the WentzelKramers-Brillouin (WKB) approximation. For l = 2 modes the situation seems much more complex.…”

Section: Preliminary Testmentioning

confidence: 97%

“…Outside these frequency ranges, the l = 2 modes have inertias that are too large for the modes to have detectable heights in the oscillation spectra, even with the longest Kepler datasets (see, e.g., Grosjean et al 2014). This makes it much harder to precisely estimate the asymptotic properties of l = 2 pure g modes, which are required if we want to apply the method of Goupil et al (2013) to l = 2 modes.…”

Section: Preliminary Testmentioning

confidence: 99%

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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: Preliminary Testmentioning

confidence: 97%

Section: Preliminary Testmentioning

confidence: 99%

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

Deheuvels

Ouazzani

Basu

2017

A&A

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“…Goupil et al (2013) propose a way to infer directly the ratio of the average envelope to core rotation rates from the observations. In this paper, we take a different approach by using forward modelling.…”

Section: Testing Of the Rotational Profile From Forward Modellingmentioning

confidence: 99%

Pulsating red giant stars in eccentric binary systems discovered fromKeplerspace-based photometry

Beck

Hambleton

Vos

et al. 2014

A&A

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132

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Context. The unparalleled photometric data obtained by NASA's Kepler Space Telescope has led to improved understanding of red giant stars and binary stars. Seismology allows us to constrain the properties of red giants. In addition to eclipsing binaries, eccentric non-eclipsing binaries that exhibit ellipsoidal modulations have been detected with Kepler. Aims. We aim to study the properties of eccentric binary systems containing a red giant star and to derive the parameters of the primary giant component. Methods. We applied asteroseismic techniques to determine the masses and radii of the primary component of each system. For a selected target, light and radial velocity curve modelling techniques were applied to extract the parameters of the system and its primary component. Stellar evolution and its effects on the evolution of the binary system were studied from theoretical models. Results. The paper presents the asteroseismic analysis of 18 pulsating red giants in eccentric binary systems, for which masses and radii were constrained. The orbital periods of these systems range from 20 to 440 days. The results of our ongoing radial velocity monitoring programme with the Hermes spectrograph reveal an eccentricity range of e = 0.2 to 0.76. As a case study we present a detailed analysis of KIC 5006817, whose rich oscillation spectrum allows for detailed seismic analysis. From seismology we constrain the rotational period of the envelope to be at least 165 d, which is roughly twice the orbital period. The stellar core rotates 13 times faster than the surface. From the spectrum and radial velocities we expect that the Doppler beaming signal should have a maximum amplitude of 300 ppm in the light curve. Fixing the mass and radius to the asteroseismically determined values, we find from our binary modelling a value of the gravity darkening exponent that is significantly larger than expected. Through binary modelling, we determine the mass of the secondary component to be 0.29 ± 0.03 M . Conclusions. For KIC 5006817 we exclude pseudo-synchronous rotation of the red giant with the orbit. The comparison of the results from seismology and modelling of the light curve shows a possible alignment of the rotational and orbital axis at the 2σ level. Red giant eccentric systems could be progenitors of cataclysmic variables and hot subdwarf B stars.

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“…How the inertia depends on the models is detailed in several other studies (e.g. Montalbán & Noels 2013) and can be understood through simple asymptotic derivations (see Goupil et al 2013, and Appendix A). The work due to non-adiabatic effects for p-type mode can be estimated with scaling relations ).…”

Section: Non-adiabatic Effects On Power Spectramentioning

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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Seismic diagnostics for transport of angular momentum in stars

Cited by 114 publications

References 31 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

Pulsating red giant stars in eccentric binary systems discovered fromKeplerspace-based photometry

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

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