Dipole low-order g-mode instability of metal-poor low-mass main-sequence stars due to the mechanism

Sonoi, T.; Shibahashi, Hiromoto

doi:10.1111/j.1365-2966.2012.20827.x

Cited by 8 publications

(5 citation statements)

References 20 publications

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“…The absence of equilibrium conditions for a prolongated portion of time after the ZAMS is due to an additional mixing, providing more nuclear fuel for the He 3 combustion. The origin of this mixing is unclear and could be due to rotation, overshooting, or even nonlinear gravity modes, although this latter case seems less plausible considering the stability analyses of Sonoi & Shibahashi (2012). The seismic data alone cannot disentangle between these processes.…”

Section: Discussionmentioning

confidence: 99%

“…The phenomenon was linked to the so-called "solar-spoon" mechanism presented by Dilke & Gough (1972) which was extensively discussed (see e.g. Ulrich & Rood 1973;Christensen-Dalsgaard et al 1974;Unno 1975;Shibahashi et al 1975, for a few references) and also investigated for Population III stars (Sonoi & Shibahashi 2012). In the latter case, the mixing results from the transport of chemicals by the nonlinear gravity modes generated by a form -mechanism due to the nuclear burning of 3 He.…”

Section: Survival Of a Convective Core In Kepler-444mentioning

confidence: 99%

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Revisiting Kepler-444

Buldgen

Farnir

Pezzotti

et al. 2019

A&A

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Context. The CoRoT and Kepler missions have paved the way for synergies between exoplanetology and asteroseismology. The use of seismic data helps providing stringent constraints on the stellar properties which directly impact the results of planetary studies. Amongst the most interesting planetary systems discovered by Kepler, Kepler-444 is unique by the quality of its seismic and classical stellar constraints. Its magnitude, age and the presence of 5 small-sized planets orbiting this target makes it an exceptional testbed for exoplanetology. Aims. We aim at providing a detailed characterization of Kepler-444, focusing on the dependency of the results on variations of key ingredients of the theoretical stellar models. This thorough study will serve as a basis for future investigations of the planetary evolution of the system orbiting Kepler-444. Methods. We use local and global minimization techniques to study the internal structure of the exoplanet-host star Kepler-444. We combine seismic observations from the Kepler mission, Gaia DR2 data, and revised spectroscopic parameters to precisely constrain its internal structure and evolution. Results. We provide updated robust and precise determinations of the fundamental parameters of Kepler-444 and demonstrate that this low-mass star bore a convective core during a significant portion of its life on the main sequence. Using seismic data, we are able to estimate the lifetime of the convective core to approximately 8 Gyr out of the 11 Gyr of the evolution of Kepler-444. The revised stellar parameters found by our thorough study are M = 0.754 ± 0.03 M⊙, R = 0.753 ± 0.01 R⊙, and Age = 11 ± 1 Gyr.

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Section: Discussionmentioning

confidence: 99%

Section: Survival Of a Convective Core In Kepler-444mentioning

confidence: 99%

Revisiting Kepler-444

Buldgen

Farnir

Pezzotti

et al. 2019

A&A

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“…Sonoi and Shibahashi (2012) found that the instability of the low-degree low-order gmodes due to the non-equilibrium 3 He burning is induced in a wider range of stellar mass as the metallicity decreases. In this case, the ratio ρ c / ρ decreases with decreasing the metallicity, since the star becomes compact as the opacity decreases.…”

Section: The -Mechanismmentioning

confidence: 99%

Stellar oscillations - II - The non-adiabatic case

Samadi

Belkacem

Sonoi

2015

EAS Publications Series

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Abstract. A leap forward has been performed due to the space-borne missions, MOST, CoRoT and Kepler. They provided a wealth of observational data, and more precisely oscillation spectra, which have been (and are still) exploited to infer the internal structure of stars. While an adiabatic approach is often sufficient to get information on the stellar equilibrium structures it is not sufficient to get a full understanding of the physics of the oscillation. Indeed, it does not permit one to answer some fundamental questions about the oscillations, such as: What are the physical mechanisms responsible for the pulsations inside stars? What determines the amplitudes? To what extent the adiabatic approximation is valid? All these questions can only be addressed by considering the energy exchanges between the oscillations and the surrounding medium.This lecture therefore aims at considering the energetical aspects of stellar pulsations with particular emphasis on the driving and damping mechanisms. To this end, the full non-adiabatic equations are introduced and thoroughly discussed. Two types of pulsation are distinguished, namely the self-excited oscillations that result from an instability and the solar-like oscillations that result from a balance between driving and damping by turbulent convection. For each type, the main physical principles are presented and illustrated using recent observations obtained with the ultra-high precision photometry space-borne missions (MOST, CoRoT and Kepler). Finally, we consider in detail the physics of scaling relations, which relates the seismic global indices with the global stellar parameters and gave birth to the development of statistical (or ensemble) asteroseismology. Indeed, several of these relations rely on the same cause: the physics of non-adiabatic oscillations.

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“…Such situation appears also in metal-poor low-mass main-sequence stars. Sonoi and Shibahashi (2012) found that the instability of the low-degree low-order gmodes due to the non-equilibrium 3 He burning is induced in a wider range of stellar mass as the metallicity decreases. In this case, the ratio ρ c / ρ decreases with decreasing the metallicity, since the star becomes compact as the opacity decreases.…”

Section: The -Mechanismmentioning

confidence: 98%

Stellar oscillations. II The non-adiabatic case

Samadi,

Belkacem,

Sonoi

2015

Preprint

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Dipole low-order g-mode instability of metal-poor low-mass main-sequence stars due to the mechanism

Cited by 8 publications

References 20 publications

Revisiting Kepler-444

Revisiting Kepler-444

Stellar oscillations - II - The non-adiabatic case

Stellar oscillations. II The non-adiabatic case

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