NEW SOLAR MODELS INCLUDING HELIOSEISMOLOGICAL CONSTRAINTS AND LIGHT-ELEMENT DEPLETION

We have computed new solar models using the same stellar evolution cod e as described in Charbonnel, Vauclair and Zahn (1992). This code, ori ginating from Geneva, now includes the computation of element. segrega tion for helium and 12 heavier isotopes. It may also include any type of mixing of the stellar gas, provided this mixing can be parametrized with an effective diffusion coefficient as a function of radius. Here we introduced rotation-induced mixing as prescribed by Zahn (1992). W e present five solar models: 1) the standard model, computed with heav y element abundances as given by Grevesse (1991); 2) a model including pure element segregation (no mixing outside the convective zone) with Grevesse (1991) as initial abundances; 3) same model as (2), but iter ated so that the final abundances are those of Grevesse (1991); 4) a m odel with both element segregation and rotation-induced mixing, leadin g to lithium and beryllium depletion consistent with the observations, with Grevesse (1991) as initial abundances; 5) same model as (4) but iterated to obtain Grevesse (1991) as final abundances. This model (5) now represents our best new solar model consistent with the observati ons. The u = P/rho function computed as a function of radius in these new solar models are compared to the helioseismological results obtain ed for the same function by Dziembowski et al (1994). Improving the ph ysics of the models leads to a better consistency with helioseismology . In our best model (5), which includes both Segregation and mixing, t he relative difference in the u function between the model and the hel ioseismological results is smaller than 0.5 per cent at all radii exce pt at the center and the surface. Meanwhile lithium is depleted by a f actor 155 and beryllium by a factor 2.9, which is consistent with the observations. The bottom of the convective zone lies at a fractional r adius of 0.716, consistent with helioseismology. The neutrino fluxes a re not decreased in any of these models. The models including the comp utations of element segregation lead to a present surface helium abund ance of: Y-sur f between 0.248 and 0.258, which is in satisfactory agr eement with the value derived from helioseismology.