Data from paper: A Chemical Mismatch Between Young Stars and Their Inner Disks

We present the first stellar elemental abundance study for two very low-mass stars, similar in mass to TRAPPIST-1, in the $\sim5-10$\,Myr-old Upper-Sco association. Their mid-infrared JWST/MIRI spectra, like those of many very low-mass stars, are hydrocarbon-rich, indicating C/O ratios greater than unity in the inner disk gas inside their snowlines. By fitting synthetic spectra to high-resolution APOGEE near-infrared stellar spectra, we show that, unlike their inner disks, both stars have solar C/O ratios. Their Fe, C, O, Mg, and Ca abundances are likewise consistent with solar values, placing them within the Galactic thin-disk population, as expected for nearby star-forming regions. This contrast between stellar and inner disk C/O ratios provides the first direct evidence that the inner disk's supersolar values are not inherited from the natal cloud but arise from disk processes. If these enhanced C/O ratios are primarily driven by inward drift of icy pebbles, there are major implications for disk evolution and planet formation, which we also discuss.

本研究首次针对两颗质量与TRAPPIST-1相当的极矮恒星，在年龄约5~10百万年的天蝎-半人马星协（Upper-Sco association）中开展恒星元素丰度研究。它们的詹姆斯·韦布空间望远镜（JWST）中红外仪器（MIRI）获取的中红外光谱，与多数极矮恒星的光谱类似，均富含烃类物质，表明其雪线内侧的内盘气体碳氧比大于1。通过将合成光谱与高分辨率APOGEE近红外恒星光谱进行拟合，我们发现：与各自的内盘不同，这两颗恒星的碳氧比与太阳一致。它们的铁、碳、氧、镁及钙元素丰度同样与太阳值相符，表明其隶属于银河薄盘星族，这与邻近恒星形成区的预期特征一致。恒星与内盘碳氧比之间的这种差异，首次直接证明了内盘的超太阳碳氧比并非继承自原恒星云，而是由盘自身演化过程所产生。若这些升高的碳氧比主要由冰质砾石的向内漂移所驱动，则将对盘演化与行星形成研究产生重大启示，本文亦对此展开讨论。