One of the main physical inputs required to solve the equations of stellar structure is the electron thermal conductivity. When the degree of electron degeneracy is significant, electron conduction is the dominant energy transport mechanism, and the value of the electron conduction opacity (proportional to the inverse of the electron thermal conductivity) enters the equation of the temperature gradient. This physical condition is verified in the interiors of brown dwarfs, very low-mass stars with the mass M<0.15M_Sun, in the He-core of low-mass stars during their Red Giant Branch (RGB) evolution, in the CO core of Asymptotic Giant Branch stars, as well as in white dwarfs (core and part of the envelopes) and envelopes of neutron stars.

The value of the electron conduction opacity is crucial in particular for the evolution of RGB low-mass stars and the fate of their progeny. Until recently, the electron-electron (ee) scattering mechanism was paid little attention in hte corresponding stellar models. However, as it has been already noted by Hubbard & Lampe (1969) and recently stressed by Catelan (2005) (astro-ph/0507464), the ee scattering can give a considerable contribution to the opacity in partially degenerate regions within the He-core of RGB stars.

We improve the previous treatments of electron thermal conductivities in RGB models by including the ee scattering in partially degenerate and nondegenerate matter. In addition, we take into account a recent improvement of the treatment of the ee scattering in degenerate matter by Shternin & Yakovlev (2006). To verify the impact of these new conductive opacities, we compute models of low-mass stars and perform a detailed analysis of the effects of the new conductive opacity evaluations on both the RGB and HB evolutionary phases. We also assess their impact on models of very low-mass stars and white dwarfs.

Page created on January 10, 2007, last updated on January 12, 2007.