Atomic diffusion in star models of type earlier than G

Morel, Pierre; Thévenin, F.

doi:10.1051/0004-6361:20020768

Cited by 49 publications

(64 citation statements)

References 42 publications

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“…In a test, we investigated the effect of mixing that results from the radiative diffusivity associated with the kinematic radiative viscosity ν rad (subset A described in Appendix A). According to Morel & Thévenin (2002), it can be modelled by adding an additional mixing with a diffusion coefficient…”

Section: Model Input Physics and Chemical Compositionmentioning

confidence: 99%

“…Cases 1, 2, 7-νrad In these models, the impact of mixing that results from the radiative diffusivity associated with the kinematic radiative viscosity is investigated. Following Morel & Thévenin (2002), we added an extra mixing diffusion coefficient d rad = D R × ν rad with D R = 1 that limits gravitational settling in the outer stellar layers of stars with thin convective envelopes.…”

Section: Cases 1-ov30mentioning

confidence: 99%

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

Lebreton

Goupil

2014

A&A

160

168

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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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Section: Model Input Physics and Chemical Compositionmentioning

confidence: 99%

Section: Cases 1-ov30mentioning

confidence: 99%

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

Lebreton

Goupil

2014

A&A

160

168

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“…In this study, we ignore the thermohaline mixing. Furthermore, we also ignore the extra mixing induced by magnetic fields, but we do include the radiative levitation based on Thoul et al (1994) and Morel & Thévenin (2002).…”

Section: Convection Overshooting and Thermohaline Mixingmentioning

confidence: 99%

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

Moravveji¹,

Guinan²,

Khosroshahi³

et al. 2013

200

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α 1 Her is the second closest asymptotic giant branch (AGB) star to the Sun, and the variable luminous M5 Ib-II member of a triple-stellar system containing G8 III and A9 IV-V components. However, the mass of this important star was previously uncertain, with published values ranging from ∼2-15 M . As shown by this study, its fortuitous membership in a nearby resolved triple-star system makes it possible to determine its fundamental properties including its mass and age. We present over 20 years of VRI photometry of α 1 Her as well as Wing intermediate-band near-IR TiO and NIR continuum photometry. We introduce a new photometry-based calibration technique and extract the effective temperature and luminosity of α 1 Her, in agreement with recent interferometric measures. We find average values of T eff = 3280 ± 87 K and log(L/L ) = 3.92 ± 0.14. With the MESA code, we calculate a dense grid of evolutionary tracks for Galactic low-to intermediate-mass (1.3 to 8 M ) rotating stars from the pre-main sequence phase to the advanced AGB phase. We include atomic diffusion and rotation mechanisms to treat the effects of extra elemental mixing. Based on the observed properties of the α Herculis stars, we constrain the age of the system to lie in the range 0.41 to 1.25 Gyr. Thus, the mass of α 1 Her lies in the range 2.175 M/M 3.250. We compare our model-based age inference with recent tracks of the Geneva and STAREVOL codes, and show their agreement. In the prescribed mass range for α 1 Her, the observed 12 C/ 13 C and 16 O/ 17 O ratios are consistent (within 2σ ) with the ratios predicted by the MESA, Geneva, and STAREVOL codes.

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“…a 1.5 M main sequence star, including radiative accelerations do not sufficiently limit the strong depletion of helium and heavy element content in the upper layers of the envelope. We follow in this paper the suggestion by Morel & Thévenin (2002) to include an additional mixing, proportional to the radiative viscosity, parametrized by 1 The detailed description can be found in "Notice de CESAM", available on request on the WEB site http://www.obs-nice.fr/morel/fichier_perso.html. D R .…”

Section: Physics Of Modelsmentioning

confidence: 99%

“…Richard et al 1996) or the use of an hypothetical mixed reservoir (Richer et al 2000). As done by Heger et al (2000) in their stellar evolutionary code, and according to the prescription of Morel & Thévenin (2002), we use an additional mixing -see Sect. 2.…”

Section: Introductionmentioning

confidence: 99%

Effect of microscopic diffusion on asteroseismic properties of intermediate-mass stars

Provost¹,

Berthomieu²,

Bigot³

et al. 2005

A&A

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Abstract.Results on the effects of microscopic diffusion on the modeling and oscillations of solar-like stars are discussed. Comparisons between models with and without microscopic diffusion, subjected to observational constraints, namely effective temperature, luminosity, surface metallicity and mass derived from photometry, spectroscopy and astrometry, are presented. We point out and discuss a signature of microscopic diffusion on the oscillation frequencies.

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Atomic diffusion in star models of type earlier than G

Cited by 49 publications

References 42 publications

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

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

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

Effect of microscopic diffusion on asteroseismic properties of intermediate-mass stars

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Atomic diffusion in star models of type earlier than G

Cited by 49 publications

References 42 publications

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

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

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M☉⩽ 8.0

Effect of microscopic diffusion on asteroseismic properties of intermediate-mass stars

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THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0