它们不会成为巨星：盖亚数据中缺失的富金属红巨星表明恒星演化被截断
They Won't Be Giants: Missing Metal-Rich RGB Stars in Gaia Data Indicate Truncated Stellar Evolution
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中文总结 AI 辅助
研究发现盖亚数据中高金属丰度亮红巨星系统性缺失，当前恒星演化模型未捕捉该金属丰度依赖的亮巨星减少趋势，相关结果对多天体物理研究有启示。
中文摘要 AI 辅助
我们结合盖亚（Gaia）XP金属丰度数据与SDSS-V、GALAH及LAMOST数据，研究不同金属丰度下的亮红巨星分支恒星种群。应用统一的选择标准和消光校正后，我们构建了[Fe/H]从-1到>0.4的金属丰度区间内的绝对星等分布。我们发现高金属丰度下亮巨星存在系统性缺失，而红团簇和低红巨星分支种群基本保持不变。该行为与高金属丰度下质量损失增强一致，可能源于双星相互作用或单星演化。这一趋势在多个巡天中均稳定存在，且在体积受限子样本（1-4千秒差距）中仍持续，表明其并非由距离或选择效应导致。基于PARSEC等时线的合成恒星种群可复现整体星等分布，但未预测到亮巨星随金属丰度下降的现象。对潜在系统误差（包括消光效应和利用疏散星团进行的金属丰度标度一致性检验）的测试均无法解释观测到的趋势，也无证据表明不同巡天间的金属丰度差异会驱动该结果。综上，这些发现表明亮红巨星数量存在金属丰度依赖的减少，而当前模型未捕捉到这一现象，该结果可能对高金属丰度恒星演化、氦白矮星形成、初始质量函数及富金属星系的紫外上升等研究具有启示意义。
英文摘要
We investigate the population of luminous red giant branch stars as a function of metallicity using Gaia XP metallicity combined with SDSS-V, GALAH, and LAMOST. After applying uniform selection criteria and extinction corrections, we construct absolute magnitude distributions across metallicity bins spanning [Fe/H] =-1 to >0.4. We find a systematic deficit of luminous giants at high metallicity, while the red clump and lower red giant branch populations remain largely unchanged. This behavior is consistent with enhanced mass loss at high metallicity, arising from either binary interactions or single-star evolution. This trend is robust across multiple surveys and persists within volume-limited subsamples (1-4 kpc), suggesting it is not driven by distance or selection effects. Synthetic stellar populations based on PARSEC isochrones reproduce the overall magnitude distributions but do not predict a decline in luminous giants with metallicity. Tests of potential systematics, including extinction effects and metallicity scale consistency using open clusters, do not account for the observed trend. We also find no evidence that survey-to-survey differences in metallicity drive the observed result. Together, these findings suggest a metallicity-dependent reduction in the number of luminous red giants that is not captured by current models. This result may have implications for stellar evolution at high metallicity, helium white dwarf formation, and the initial mass function as well as the UV upturn in metal-rich galaxies.
