行星宿主恒星TRAPPIST-1的同位素与元素丰度
The Isotopic and Elemental Abundances of Planet-Host Star TRAPPIST-1
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中文总结 AI 辅助
本研究通过分析TRAPPIST-1的近红外高分辨率光谱，首次测定其碳氧比、碳及氧同位素比等关键化学丰度，发现其丰度总体类太阳但¹²C/¹³C略高于太阳。
中文摘要 AI 辅助
元素与同位素丰度是追踪行星形成、恒星演化及银河系化学演化的关键示踪剂。在这方面，极矮星尤为受关注，因为与质量更大或已演化的恒星不同，它们的光球层丰度保留了恒星的初始组成。长期以来，冷矮星的光谱因分子与原子特征混叠，一直难以用于化学丰度测量。不过，近期分子线表、大气模型、拟合技术及红外摄谱仪的进展，已成功实现对数十颗极矮星的元素与同位素比率测量。本研究呈现了TRAPPIST-1的近红外高分辨率光谱，覆盖一氧化碳及其主要同位素体的基频与泛音带。通过联合分析K波段（CFHT/SPIRou）与M波段（Keck/NIRSPEC）光谱，首次测定了该恒星的恒星碳氧比、碳同位素比及氧同位素比。得到金属丰度[M/H]=0.00±0.06，碳氧比为0.60±0.02，¹²C/¹³C=154⁺¹⁷₋₁₆，¹⁶O/¹⁸O=490⁺⁷⁸₋₆₄。TRAPPIST-1的元素丰度总体类似太阳，其¹²C/¹³C比率高于太阳值，且相对于一些同金属丰度的邻近冷矮星可能略有升高；碳氧比主要由K波段数据精确约束，同位素检测则由M波段数据主导。
英文摘要
Elemental and isotopic abundances are key tracers of planet formation, stellar evolution, and Galactic chemical evolution. Very low-mass stars are particularly interesting in this regard, because unlike more massive or evolved stars their photospheric abundances retain the star's natal composition. Cool dwarf spectra have historically been challenging to use for measurements of chemical abundances because of the blending of molecular and atomic features. However, recent advances in molecular line lists, atmospheric models, fitting techniques and IR spectrographs have enabled the successful measurement of elemental and isotopic ratios in a few dozen very low-mass stars. Here, we present near-infrared high-resolution spectroscopy of TRAPPIST-1 covering the fundamental and overtone bands of carbon monoxide and its prominent isotopologues. From the joint analysis of the $K$-band (CFHT/SPIRou) and $M$-band (Keck/NIRSPEC) spectra, we derive the first stellar C/O ratio and the first carbon and oxygen isotope ratios for this star. We obtain a metallicity of $[\mathrm{M/H}] = 0.00 \pm 0.06$, a C/O ratio of $0.60 \pm 0.02$, $^{12}\mathrm{C}/^{13}\mathrm{C} = 154{}^{+17}_{-16}$, and $^{16}\mathrm{O}/^{18}\mathrm{O} = 490{}^{+78}_{-64}$. TRAPPIST-1 has generally solar-like elemental abundances, with a $^{12}\mathrm{C}/^{13}\mathrm{C}$ ratio that is higher than the solar value and may be modestly elevated relative to some nearby cool dwarfs at similar metallicity. While C/O is most tightly constrained by the $K$-band, the isotopic detections are driven by the $M$-band data.
发表机构
- Leiden Observatory, Leiden University（莱顿天文台，莱顿大学）
- Department of Physics and Astronomy, University of Kansas（堪萨斯大学物理与天文学系）
- Department of Physics and Astronomy, University of New Mexico（新墨西哥大学物理与天文学系）
- Space Telescope Science Institute（太空望远镜科学研究所）
- Department of Earth Sciences, University of Hawai’i at Mānoa（夏威夷大学马诺阿分校地球科学系）
- INAF-Osservatorio di Astrofisica e Scienza dello Spazio（意大利国家天体物理研究所空间科学与天体物理观测台）
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