AI 中文总结
利用SDSS/APOGEE数据研究开放星团NGC 752和鲁普雷希特147中恒星的原子扩散，分析多种元素丰度差异，拟合观测模式获星团年龄，碳为关键诊断元素，结果进一步约束原子扩散模型，影响主序拐点附近恒星年龄估计。
AI 中文摘要
对随时间改变表面化学丰度的恒星过程的不断理解，为利用这些变化探测恒星性质开辟了新途径。在主序和接近拐点处，恒星表面丰度受引力沉降和辐射加速影响，统称为原子扩散。本文利用SDSS/APOGEE DR17/DR19数据研究开放星团NGC 752和鲁普雷希特147中的原子扩散，以确定这些特征如何随年龄变化。通过对多种元素分析，发现拐点附近恒星与较冷主序星存在显著丰度差异，符合原子扩散预期特征。通过拟合观测模式获得星团年龄，碳是关键诊断元素。研究结果进一步约束了原子扩散模型，表明其影响主序拐点附近恒星的年龄估计。
英文摘要
A growing understanding of stellar processes that alter surface chemical abundances over time has opened new avenues for using these changes as probes of stellar properties. On the main sequence and near the turnoff, stellar surface abundances are affected by gravitational settling and radiative acceleration, collectively known as atomic diffusion. In this work, we use SDSS/APOGEE DR17/DR19 data to investigate atomic diffusion in the open clusters NGC~752 and Ruprecht~147, thereby constraining how these signatures vary with age. From the analysis of Fe, C, N, Na, Mg, Al, Si, S, K, Ca, Ti, V, Cr, Mn, Co, and Ni, we find significant abundance differences between stars near the turnoff and the cooler main-sequence, where warmer stars are depleted relative to the cooler main-sequence stars at the $\geq1σ$ level for all elements available in the analysis. These abundance differences are consistent with the signatures expected from atomic diffusion and are further supported by comparisons with stellar models that include diffusion. By fitting the observed $T_{\rm eff}$--[Fe/H] patterns with MIST isochrones, we obtain best-fit ages of 1.0~Gyr for NGC~752 and 2.5--3.2~Gyr for Ruprecht~147. Carbon is a key diagnostic, as it shows both atomic diffusion and extra-mixing signatures associated with first-dredge-up. For NGC~752, the coolest stars in our sample, which provide the best proxy for the initial cluster composition, yield [Fe/H]$_{\rm CS} = 0.01~\pm~0.02(\pm~0.05)$ dex. For Ruprecht~147, we obtain [Fe/H]$_{\rm CS} = 0.17~\pm~0.00(\pm~0.05)$ dex. Our findings further constrain atomic diffusion models, suggesting that atomic diffusion affects age estimates of stars near the main-sequence turnoff.
CommentsAccepted for publication in the ApJ
