A data-driven estimate of the protosolar helium mass fraction

Abstract

The protosolar helium mass-fraction is a key ingredient of solar, planetary models and enrichment laws. However, the assumed values often rely on simplified descriptions of the transport of chemicals in solar models. They are also based on the inferred helium mass fraction in the solar convective envelope, which is itself sensitive to uncertainties in the solar equation of state. We update the reference protosolar helium abundance by including the effects of macroscopic mixing at the base of the convective zone and more recent determinations of the helium mass fraction in the convective envelope. We combine results from our inversions to spectroscopic abundances, as well as literature values to provide a robust interval of the current helium mass fraction in the convective zone. We combine this measurement to models including light element depletion to provide an udpated protosolar helium abundance. We show that macroscopic mixing at the base of the envelope is key to infer protosolar helium. We find a revised interval of primordial helium mass fraction of 0.27575 +- 0.00315 slightly lower than previous estimates when combining our latest estimate of surface helium mass fraction and spectroscopic abundances. We find that the effects of macroscopic mixing are partially compensated by an increase in the inferred solar helium mass fraction in recent studies. We also derive more precise estimates based on various reference works in the litterature. Using the usual surface helium mass fraction, the primordial helium mass fraction drops to 0.2669 +- 0.00415 due to the inclusion of macroscopic mixing. The dominant source of uncertainty is found the surface helium abundance inferred from helioseismic constraints and more specifically, the impact on the equation of state of the solar material on this inference result.

Accepted for publication in Astronomy and Astrophysics

References in corpus (29)

• The chemical make-up of the Sun: A 2020 vision
• Element Diffusion in the Solar Interior
• NACRE II: an update of the NACRE compilation of charged-particle-induced thermonuclear reaction rates for nuclei with mass number $A<16$
• New Solar Composition: The Problem With Solar Models Revisited
• Constraining solar abundances using helioseismology
• A New Generation of Los Alamos Opacity Tables
• Observational constraints on the origin of the elements. IV: The standard composition of the Sun
• On the opacity change required to compensate for the revised solar composition
• Solar structure and evolution
• 3D NLTE spectral line formation of lithium in late-type stars
• Determining the initial helium abundance of the Sun
• New Constraints on the Composition of Jupiter from Galileo Measurements and Interior Models
• Seismic tests for solar models with tachocline mixing
• An Exploration of Double Diffusive Convection in Jupiter as a Result of Hydrogen-Helium Phase Separation
• On the choice of parameters in solar structure inversion
• Solar models with convective overshoot, the solar-wind mass loss, and a PMS disk accretion: helioseismic quantities, Li depletion and neutrino fluxes
• A synoptic comparison of the MHD and the OPAL equations of state
• Bayesian Evolution Models for Jupiter with Helium Rain and Double-diffusive Convection
• Combining multiple structural inversions to constrain the Solar modelling problem
• Evolution of Jupiter and Saturn with helium rain
• Higher metal abundances do not solve the solar problem
• On the hydrostatic stratification of the solar tachocline
• Imprint of planet formation in the deep interior of the Sun
• Evidence of a signature of planet formation processes from solar neutrino fluxes
• Helioseismic Measurements in the Solar Envelope Using Group Velocities of Surface Waves
• Constraints on the properties of macroscopic transport in the Sun from combined lithium and beryllium depletion
• Ionization of heavy elements and the adiabatic exponent in the solar plasma
• Solar models with protosolar accretion and turbulent mixing
• The impact of the transport of chemicals and electronic screening on helioseismic and neutrino observations in solar models