星际彗星3I/ATLAS的多波长近日点后偏振观测
Multi-Wavelength Post-Perihelion Polarimetry of Interstellar Comet 3I/ATLAS
另 5 家 · 查看机构详情
- University of Helsinki（赫尔辛基大学）
- Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences（保加利亚科学院天文研究所与国家天文台）
- Armagh Observatory & Planetarium（阿马天文台与天文馆）
- University of Maryland（马里兰大学）
- TU Braunschweig（布伦瑞克工业大学）
- INAF – Osservatorio Astrofisico di Torino（意大利国家天体物理研究所都灵天文台）
- Finnish Centre for Astronomy with ESO, University of Turku（图卢大学ESO芬兰天文学中心）
- Luleå University of Technology（吕勒奥理工大学）
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中文总结 AI 辅助
本研究对星际彗星3I/ATLAS开展多波长近日点后偏振观测，扩大相位角覆盖范围，约束其最小偏振度，揭示偏振的波长依赖性，通过数值模拟解释其特殊偏振特性的成因。
中文摘要 AI 辅助
我们利用甚大望远镜的FORS2、北欧光学望远镜的ALFOSC以及2米里奇-克雷蒂安-库德望远镜的FoReRo2，对第三颗被发现的星际天体3I/ATLAS（C/2025 N1，以下简称3I）开展了新的近日点后偏振观测。观测覆盖相位角1°至30°，是迄今获得的星际天体中最广泛的偏振相位角覆盖范围。近日点后测量显示，3I的特殊偏振特性在近日点前后持续存在，且与近期独立的近日点后观测结果吻合，表明偏振特性无显著演化。扩大的相位角覆盖范围使我们能进一步将最小偏振度限制为相位角5.5°时的-2.9%。多波段BVRI观测揭示了偏振的波长依赖性：在更长波长下，负偏振分支变得更深且向更小相位角偏移。偏振色主要呈红色，且随相位角增大而增加，与其他彗星的观测行为一致。成像和偏振图显示，近日点后彗发明显更延展，而偏振分布本身保持平滑且空间均匀。数值模拟表明，异常深的偏振相位曲线源于由弱吸收亚微米单体组成的中等多孔尘埃聚集体，其产生的尘埃亮度远高于典型太阳系彗星中的尘埃。
英文摘要
We present new post-perihelion polarimetric observations of the third discovered interstellar object, 3I/ATLAS (C/2025 N1; hereafter 3I), obtained using FORS2 at the Very Large Telescope, ALFOSC at the Nordic Optical Telescope, and FoReRo2 at the 2 m Ritchey-Chrétien-Coudé telescope. The observations span phase angles 1-30$^{\circ}$, providing the most extensive polarimetric phase angle coverage obtained for an interstellar object to date. The post-perihelion measurements reveal that the unusual polarimetric properties of 3I persist across perihelion and match recent independent post-perihelion observations, indicating no significant evolution in the polarimetric properties. The increased phase angle coverage allowed us to further constrain the minimum polarisation to $-2.9\%$ at phase angle $5.5^{\circ}$. Multi-band BVRI observations reveal a wavelength dependence of polarisation, with the negative polarisation branch becoming deeper and shifted toward smaller phase angles at longer wavelengths. The polarimetric colour is predominantly red and increases with phase angle, consistent with behaviour observed in other comets. Imaging and polarimetric maps show a substantially more extended coma after perihelion, while the polarisation distribution itself remains smooth and spatially homogeneous. Numerical modelling suggests that the unusually deep polarisation phase curve originates from moderately porous dust aggregates consisting of weakly absorbing sub-micron monomers, resulting in much brighter dust than that in typical solar system comets.
