高分辨率光谱揭示星际彗星3I/ATLAS独特的挥发性成分

中文摘要 AI 辅助

彗星保存着行星系统形成早期的挥发性物质。星际彗星3I/ATLAS的发现使得直接比较围绕其他恒星形成的彗星与太阳系彗星成为可能。我们利用ESO甚大望远镜上的UVES光谱仪，通过均匀的高分辨率近紫外和光学光谱，表征了3I/ATLAS在过近日点前后的彗发成分，观测时间从2025年8月（r_h=3.14 au）过近日点前到2026年2月（r_h=4.34 au）过近日点后。基于流量定标光谱，我们测量了OH、NH、CN、C$_3$、CH和C$_2$的发射，推导了产率，检验了丰度比和日心距离趋势，约束了NH$_2$，并将基于OH的水产率与禁戒氧线的估计值进行了比较。气体产率显示出过近日点前后大致对称的行为，其日心距离依赖关系比太阳系彗星中通常观测到的更陡峭。NH和NH$_2$强烈贫乏，表明与氨相关的挥发性物质严重缺乏。C$_2$/CN比率表明碳链贫乏，并随日心距离演化，这与彗发驱动效应（如过度活跃）一致，而非内在成分变化。除近日点附近外，禁戒氧线得出的水产率超过基于OH的估计值，表明H$_2$O和CO$_2$对彗发化学的贡献存在变化。相对丰度相关性将3I/ATLAS置于典型太阳系彗星群之外，与碳链强烈贫乏的彗星（包括G-Z型彗星）最为接近，同时相对于CN显示出NH和C$_3$携带物种的强烈贫乏。因此，3I/ATLAS扩展了已知的彗星成分多样性，证明其他行星系统中的挥发性储库可能与太阳系彗星所采样的储库存在显著差异。

英文摘要

Comets preserve volatile material from the early stages of planetary-system formation. The discovery of the interstellar comet 3I/ATLAS enables a direct comparison between a comet formed around another star and comets in the Solar System. We characterise the coma composition of 3I/ATLAS across perihelion using homogeneous high-resolution near-UV and optical spectroscopy with UVES on the ESO Very Large Telescope, from August 2025 (r$_h$=3.14 au) pre-perihelion to February 2026 (r$_h$=4.34 au) post-perihelion. From flux-calibrated spectra, we measured OH, NH, CN, C$_3$, CH and C$_2$ emissions, derived production rates, examined abundance ratios and heliocentric-distance trends, constrained NH$_2$, and compared OH-based water production with estimates from forbidden oxygen lines. Gas production rates show broadly symmetric pre- and post-perihelion behaviour, with steeper heliocentric-distance dependences than typically observed in Solar System comets. NH and NH$_2$ are strongly depleted, indicating a severe deficiency of ammonia-related volatiles. The C$_2$/CN ratio indicates carbon-chain depletion and evolves with heliocentric distance, consistent with coma-driven effects such as hyperactivity rather than intrinsic compositional changes. Water production from forbidden oxygen lines exceeds OH-based estimates except near perihelion, suggesting varying contributions from H$_2$O and CO$_2$ to coma chemistry. Relative abundance correlations place 3I/ATLAS outside the canonical Solar System comet cluster and closest to strongly carbon-chain depleted comets, including G-Z-type comets, while showing strong depletion of NH- and C$_3$-bearing species relative to CN. 3I/ATLAS therefore extends the known diversity of cometary compositions, demonstrating that volatile reservoirs in other planetary systems can differ substantially from those sampled by Solar System comets.

发表机构

• STAR Institute, Université de Liège（列日大学STAR研究所）
• Institute for Astronomy, University of Edinburgh, Royal Observatory（爱丁堡大学天文研究所皇家天文台）
• Physics Department, Edmund C. Leach Science Center, Auburn University（奥本大学艾德蒙·C·利奇科学中心物理系）
• School of Physical and Chemical Sciences – Te Kura Matū, University of Canterbury（坎特伯雷大学物理与化学科学学院）
• Faculty of Science and Engineering, Northumbria University（诺森比亚大学科学与工程学部）
• Koyama Space Science Institute, Kyoto Sangyo University（京都产业大学小山宇宙科学研究所）
• INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）

机构由 AI 辅助整理，请以论文原文为准。

补充信息

备注

16 pages (4 page appendix), 13 Figures, 4 Tables, Accepted for publication in A&A