Diffusion coefficients for stellar plasmas

Paquette, C.; Pelletier, C.; Fontaine, G.; Michaud, G.

doi:10.1086/191111

Cited by 333 publications

(426 citation statements)

References 0 publications

Supporting

Mentioning

409

Contrasting

Unclassified

Order By: Relevance

“…The modelling was done with the TGEC (ToulouseGeneva stellar evolution code). Atomic diffusion was included in all the models using the formalism derived by Paquette et al (1986), as explained by Richard et al (2004). The treatment of convection was done in the framework of the mixing-length theory, and the mixing-length parameter was adjusted as in the Sun.…”

Section: The "Old Times"mentioning

confidence: 99%

Seismic studies of planet-harbouring stars

Vauclair¹

2013

Proc. IAU

View full text Add to dashboard Cite

Abstract. During the past decades, stellar oscillations and exoplanet searches were developed in parallel, and the observations were done with the same instruments: radial velocity method, essentially with ground-based instruments, and photometric methods (light curves) from space. The same observational data on one star could lead to planet discoveries at large time scales (days to years) and to the detection of stellar oscillations at small time scales (minutes), such as for the star μ Arae. Since the beginning, it seemed interesting to investigate the differences between stars with and without observed planets. Also, a precise determination of the stellar parameters is important to characterize the detected exoplanets. With the thousands of exoplanet candidates discovered by Kepler, automatic procedures and pipelines are needed with large data bases to characterize the central stars. However, precise asteroseismic studies of well-chosen stars are still important for a deeper insight.

show abstract

Section: The "Old Times"mentioning

confidence: 99%

Seismic studies of planet-harbouring stars

Vauclair¹

2013

Proc. IAU

View full text Add to dashboard Cite

show abstract

“…Cox et al 1989;Proffitt & Michaud 1991;Michaud & Proffit 1993;Thoul et al 1994). But, in the standard framework of the calculation of collision integrals and resistance coefficients (Burgers 1969;Paquette et al 1986), only the ion-ion and electron-ion collisions are taken into account and the derived diffusivity corresponds only to ν mol .…”

Section: Radiative Diffusivitymentioning

confidence: 99%

“…The charge of a given isotope is taken as the average 2 charge over all its ionization states. The collision integrals and resistance coefficients are taken from the tabulations of Paquette et al (1986). For each ion, the coefficient of radiative diffusivity is added to the coefficient of molecular diffusivity.…”

Section: Computation Of Models and Physical Inputsmentioning

confidence: 99%

Atomic diffusion in star models of type earlier than G

Morel

Thévenin

2002

A&A

View full text Add to dashboard Cite

Abstract. We introduce the mixing resulting from the radiative diffusivity associated with the radiative viscosity in the calculation of stellar evolution models. We find that the radiative diffusivity significantly diminishes the efficiency of the gravitational settling in the external layers of stellar models corresponding to types earlier than ≈G. The surface abundances of chemical species predicted by the models are successfully compared with the abundances determined in members of the Hyades open cluster. Our modeling depends on an efficiency parameter, which is evaluated to a value close to unity, that we calibrate in this study.

show abstract

“…The thermal di usion coe cient 1i is computed using the formalism of Paquette et al 1986; A i and Z i represent the atomic mass numberand charge of element i and m H is the atomic hydrogen mass.M and R stand for the stellar mass and radius. A normalisation condition on the mass fractions of all the elements has to be added to correct for the center-of-mass displacement.…”

Section: The Diffusion Equationmentioning

confidence: 99%

“…Average values of the shielding factor were used for analytical ts of the resulting di usion coe cients. Paquette et al (1986) proposed a more precise treatment of this problem. They pointed out that the Debye shielding length has no physical meaning as soon as it is smaller than the inter-ionic distance.…”

Section: The Treatment Of Collisionsmentioning

confidence: 99%

Element Settling in the Solar Interior

Vauclair¹

1998

Solar Composition and Its Evolution — From Core to Corona

View full text Add to dashboard Cite

Abstract.Element settling inside the Sun now becomes detectable from the comparison of the observed oscillation modes with the results of the theoretical models. This settling is due, not only to gravitation, but also to thermal di usion and radiative acceleration (although this last e ect is small compared to the two others ). It leads to abundance variations of helium and heavy elements of = 10% below the convective zone. Although not observable from spectroscopy, such v ariations lead to non-negligible modi cations of the solar internal structure and evolution. Helioseismology is a powerful tool to detect such e ects, and its positive results represent a great success for the theory of stellar evolution. Meanwhile, evidences are obtained that the element settling is slightly smoothed down, probably due to mild macroscopic motions below the convective zone. Additional observations of the abundances of both 7 Li and 3 He lead to speci c constraints on these particular motions.

show abstract

Diffusion coefficients for stellar plasmas

Cited by 333 publications

References 0 publications

Seismic studies of planet-harbouring stars

Seismic studies of planet-harbouring stars

Atomic diffusion in star models of type earlier than G

Element Settling in the Solar Interior

Contact Info

Product

Resources

About