Solar Models with Convective Overshoot, Solar-wind Mass Loss, and PMS Disk Accretion: Helioseismic Quantities, Li Depletion, and Neutrino Fluxes

Abstract

Helioseismic observations have revealed many properties of the Sun: the depth and the helium abundance of the convection zone, the sound-speed and the density profiles in the solar interior. Those constraints have been used to judge the stellar evolution theory. With the old solar composition (e.g., GS98), the solar standard model is in reasonable agreement with the helioseismic constraints. However, a solar model with revised composition (e.g., AGSS09) with low abundance Z of heavy elements cannot be consistent with those constraints. This is the so-called "solar abundance problem", standing for more than ten years even with the recent upward revised Ne abundance. Many mechanisms have been proposed to mitigate the problem. However, there is still not a low-Z solar model satisfying all helioseismic constraints. In this paper, we report a possible solution to the solar abundance problem. With some extra physical processes that are not included in the standard model, solar models can be significantly improved. Our new solar models with convective overshoot, the solar wind, and an early mass accretion show consistency with helioseismic constraints, the solar Li abundance, and observations of solar neutrino fluxes.

On Stellar Evolution in a Neutrino Hertzsprung–Russell Diagram

“…We adopt a small amount of exponential convective overshooting (Herwig 2000) by choosing f ov = 0.016 as used in the MIST isochrones (Choi et al 2016). Separate implementations of convective overshooting at the base of the solar convection zone can be found in Christensen-Dalsgaard et al (2011) and Zhang et al (2019). Our calibrated solar models do not include the structural ef-fects of rotational deformation or the effects of rotational mixing.…”

The Gaia-ESO survey: 3D NLTE abundances in the open cluster NGC 2420 suggest atomic diffusion and turbulent mixing are at the origin of chemical abundance variations

“…Earlier theoretical studies of atomic diffusion and mixing in stellar structure calculations (Richard et al 2002;Deliyannis & Pinsonneault 1990;Proffitt & Michaud 1991;Richer et al 1992;Vauclair 1999;Chaboyer et al 2001;Richard 2005) are now being superseded by the new generation of stellar evolution models (e.g. Théado et al 2009;Vick et al 2013;Zhang et al 2019;Deal et al 2020) that include both atomic diffusion and transport processes as thermohaline convection, mass loss, rotation, or accretion. A comprehensive review of the subject can be found in Salaris & Cassisi (2017).…”

Solar structure and evolution

“…In Sect. 6.5 I return to this issue, based on complex modelling by Zhang et al (2019) including early accretion, mass loss and turbulent mixing.…”

“…A comprehensive effort to match observational data for the Sun, given the revised solar composition, was carried out by Zhang et al (2019), involving both pre-main-sequence accretion and early mass loss. In addition to the helioseismic data, the models were also fitted to the observed lithium abundance (see also Sect.…”

“…The most novel aspects of the model were the inclusion of Fig. 62 Results of helioseismic inversions, for Model TWA of Zhang et al (2019), including mixing below the convection zone and chemically differentiated accretion and mass loss in early phases of stellar evolution. The symbols show inferred relative differences in squared sound speed (top) and density (bottom) between the Sun and the model.…”