A New Generation of Standard Solar Models

Abstract

We compute a new generation of standard solar models (SSMs) that includes recent updates on some important nuclear reaction rates and a more consistent treatment of the equation of state. Models also include a novel and flexible treatment of opacity uncertainties based on opacity kernels, required in the light of recent theoretical and experimental works on radiative opacity. Two large sets of SSMs, each based on a different canonical set of solar abundances with high and low metallicity (Z), are computed to determine model uncertainties and correlations among different observables. We present detailed comparisons of high-and low-Z models against different ensembles of solar observables including solar neutrinos, surface helium abundance, depth of convective envelope and sound speed profile. A global comparison, including all observables, yields a p-value of 2.7σ for the high-Z model and 4.7σ for the low-Z one. When the sound-speed differences in the narrow region of 0.65 < r/R ⊙ < 0.70 are excluded from the analysis, results are 0.9σ and 3.0σ for high-and low-Z models respectively. These results show that: high-Z models agree well with solar data but have a systematic problem right below the bottom of the convective envelope linked to steepness of molecular weight and temperature gradients, and that low-Z models lead to a much more general disagreement with solar data. We also show that, while simple parametrizations of opacity uncertainties can strongly alleviate the solar abundance problem, they are insufficient to substantially improve the agreement of SSMs with helioseismic data beyond that obtained for high-Z models due to the intrinsic correlations of theoretical predictions.

The brightness of the red giant branch tip

“…While standard solar models routinely include microscopic diffusion (e.g. Vinyoles et al 2017), it is also true that helioseismic constraints favor a smaller (∼ 10-20%) effective rate than predicted by fully efficient diffusion models Delahaye & Pinsonneault (2006); Villante et al (2014). The indication that diffusion is too efficient is even more compelling in metal-poor stars and has led to the introduction ad-hoc reciped for extra-mixing (Richard et al 2002;VandenBerg et al 2012).…”

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“…The most recent and accurate version of the SSM to date is documented in [13]. The two models for solar abundances used there lead to significantly different predictions for helioseismic observations: the one with higher metallicity, called there B16-GS98, compares reasonably well with these observations; the other one with low metallicity does not [13].…”

“…Therefore, this will be used in the following. This implies a slight change of certain SSM fluxes and more precisely a downward shift of the 8 B and of the 7 Be fluxes by 2.7 and 2.8 % respectively [13]; note incidentally that this improves even further the agreement of the central values in Eq. (7).…”

“…The two models for solar abundances used there lead to significantly different predictions for helioseismic observations: the one with higher metallicity, called there B16-GS98, compares reasonably well with these observations; the other one with low metallicity does not [13]. For this reason, we adopt the expectations of the former version of the SSM for the pp and for the pep-neutrinos,…”

“…where the numerical values of the fluxes of the pp and pep neutrinos are from high metallicity SSM (version B16-GS98), as given in Table 5 of [13], and the other two are discussed above.…”