[论文解读] Does the solar oxygen abundance change over the solar cycle? An investigation into activity-induced variations of the O I infrared triplet

A. G. M. Pietrow, M. Baratella+3 more|arXiv (Cornell University)|Jan 22, 2026

Stellar, planetary, and galactic studies被引用 0

一句话总结

该研究分析两十年的太阳作为星光谱，以检验从 O I 红外三重线推断的太阳氧丰度是否随太阳周期变化；仅在 PEPSI 数据中发现微小且统计显著的 EW 变化，表明在典型不确定度内丰度变化可忽略。

ABSTRACT

The determination of the solar oxygen abundance remains a central problem in astrophysics, as its accuracy is limited not only by models but also by systematics. While many of these factors have been thoroughly characterized, the effect of the solar activity cycle has so far remained unexplored. Due to its relative strength and accessibility, the O I infrared triplet is typically the primary choice for abundance studies. However, previous investigations have shown that abundances inferred from this triplet tend to be higher than expected on active stars, whereas such an overabundance effect is not observed for the much weaker forbidden O I 6300 Å line. This raises the question of whether a similar trend can be found for the Sun. To address this question, we analyze two decades' worth of synoptic disk-integrated Sun-as-a-star datasets from the FEROS, HARPS-N, PEPSI, and NEID spectrographs, focusing on the infrared triplet (7772, 7774, 7775 Å) and the forbidden O I 6300 Å line. The excellent signal-to-noise ratio of the PEPSI observations allows us to detect a weak but significant variation in the equivalent widths of the infrared triplet, corresponding to about 0.01 dex difference in abundance between activity minimum and maximum. This value is significantly smaller than the typical uncertainties on the solar oxygen abundance. Due to higher scatter, no comparable trend is found in the other data sets. Based on these results, we conclude that within the typical uncertainties presented in other works, we can assume the inferred solar oxygen abundance to be stable across the solar cycle, but that this effect may be significant for other, more active stars.

研究动机与目标

• 评估太阳 O 丰度是否随太阳活动周期变化。
• 量化活动引起的 O I 红外三重线和禁限线 O I 6300 Å 的变化。
• 对多组太阳作为星星的数据集进行横向比较，以识别一致趋势。

提出的方法

• 使用 ARES v2 测量 O I 7772、7774、7775 Å 三重线和 O I 6300 Å 线的等效宽度（EW）。
• 按信噪比排序数据，并在接近本地中午、15 日前后3天内选择月度高S/N观测。
• 计算 EW 与太阳活动（斑数）的 Pearson 相关系数。
• 将数据分为活动组（斑数 ≥ 50）和静默组（斑数 < 50），比较中位数。
• 利用 Steffen et al. (2015) 的 3D NLTE 生长曲线，将 EW 差异转换为丰度变化 A(O)。
• 讨论检测微小变化的局限性与仪器特定精度。

实验结果

研究问题

• RQ1 在 Sun-as-a-star 观测中，O I 红外三重线的 EW 是否随太阳活动周期而呈现统计显著变化？
• RQ2 在典型丰度不确定度内，来自 O I 三重线的太阳 A(O) 是否在整个太阳周期内保持稳定？
• RQ3 相对于三重线，O I 6300 Å 禁限线对太阳活动的响应如何，是否能揭示活动引起的丰度偏差？

主要发现

• PEPSI 数据显示 O I 红外三重线随太阳活动相关的 EW 变化较弱但显著，相当于约 0.01 dex 的 A(O)。
• FEROS 和 NEID 数据未显示红外三重线的显著 EW-活动相关性。
• O I 6300 Å 禁限线在 HARPS-N 或 PEPSI 数据中对太阳活动未显示趋势。
• 0.01 dex 的丰度变化对应 PEPSI 数据中红外三重线大约 1 mÅ 的 EW 差异。
• 总体而言，太阳周期内的太阳 O 丰度在 A(O) 确定的典型不确定度内保持稳定；在其他恒星上若活动性更强，可能放大此类效应。
• 研究指出检测到的活动印记可能太小而不足以影响太阳 O 丰度研究，但可能会对更活跃星体的分析产生偏差。