从太阳包层第一绝热指数推断重元素丰度
Heavy Elements Abundances Inferred from the First Adiabatic Exponent in the Solar Envelope
AI总结：
本研究利用日震反演得到的高精度第一绝热指数剖面，通过SAHA-S物态方程合成剖面拟合，测定了太阳对流区主要重元素的丰度，结果与光谱观测值相符。
摘要：
本研究聚焦于沿绝热坐标$(T, ρ)$计算的第一绝热指数剖面（记为$Γ_1$）。在氢和氦几乎完全电离的条件下，$Γ_1$剖面对重元素电离十分敏感，在元素部分电离的区域$Γ_1$会下降。近期的日震结构反演在大部分绝热对流区的精度优于$10^{-4}$，使得研究电离变化成为可能。本研究旨在确定太阳对流区的主要重元素含量。\n我们的研究方法是$Γ_1$剖面合成法，该方法基于各重元素贡献的线性组合，这一思路由Baturin等人（Astron. Astrophys., 660, A125, 2022）提出并验证。我们固定比氖更重元素的丰度，通过调整主要元素（C、N、O、Ne）的丰度，得到反演$Γ_1$剖面的最佳近似。我们使用SAHA-S物态方程合成理论$Γ_1$剖面，能够以$(1-2)\times 10^{-5}$的精度重现反演剖面。\n通过该方法得到的重元素总质量分数为$Z=0.0148\boldsymbol{\u00b1}0.0004$；氧的对数丰度为$8.70\boldsymbol{\u00b1}0.03$，碳为$8.44\boldsymbol{\u00b1}0.04$，氮为$8.12\boldsymbol{\u00b1}0.08$，氖为$8.17\boldsymbol{\u00b1}0.09$。所得的氧和碳丰度估计值与Asplund等人（Astron. Astrophys., 653, A141, 2021）的光谱丰度结果一致。
英文摘要：
The first adiabatic exponent profile, noted $Γ_1$, computed along adiabatic coordinates $(T, ρ)$ is in the focus of our study. Under conditions of almost fully ionized hydrogen and helium, the $Γ_1$ profile is quite sensitive to heavy elements ionization. $Γ_1$ decreases in regions where an element is partially ionized. The recent helioseismic structural inversion is obtained with an accuracy better than $10^{-4}$ in the most of the adiabatic convective zone that allows to study ionization variations. The aim is to determine the major heavy elements content in the solar convective zone. The method of our research is synthesis of the $Γ_1$ profile which is based on a linear combination of the contributions of individual heavy elements. The idea of the approach was proposed and justified by Baturin et al. (Astron. Astrophys., 660, A125, 2022). We find the best approximation of the inverted profile $Γ_1$ adjusting the abundances of major elements (C, N, O, Ne), meanwhile the abundances of elements heavier than neon are fixed. We synthesize the theoretical $Γ_1$ profile using the SAHA-S equation of state, and are able to reproduce the inverted profiles with an accuracy of $(1-2)\cdot 10^{-5}$. Total mass fraction of heavy elements found by this method is $Z=0.0148\pm 0.0004$. The oxygen logarithmic abundance is $8.70\pm 0.03$, carbon $8.44\pm 0.04$, nitrogen $8.12\pm 0.08$, and neon $8.17\pm 0.09$. The obtained estimations of oxygen and carbon agree with spectroscopic abundances by Asplund et al. (Astron. Astrophys., 653, A141, 2021).
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