AI 中文总结
研究星际彗星2I/鲍里索夫的成像、光谱等观测数据，发现其化学成分与随日心距变化的行为异常，相关比值变化幅度在洛厄尔天文台彗星数据库中前所未见。
AI 中文摘要
我们报告了2019年9月13日至12月16日期间洛厄尔天文台对星际彗星2I/鲍里索夫（2I/Borisov）开展的成像、光谱及窄带测光观测结果。我们在近日点前的四个夜晚（10月4日至11月25日，日心距2.466至2.028天文单位）测量了其化学成分，所有夜晚均检测到了氰（CN）。10月27日的测量结果是目前已报道的最早的C₂和C₃检测，其中C₂与CN的对数产率比为-0.7，C₃与CN的对数产率比为-1.3。到11月25日，这两个比值均增加了近4倍，分别达到-0.3和-0.9，这种随日心距变化的增长幅度在洛厄尔天文台彗星数据库中是前所未有的。我们还在11月25日观测到了羟基（OH）和氨基（NH），由此推导出水（H₂O）的产率为4.5×10²⁶摩尔每秒，且CN与OH的对数产率比为-2.0，NH与OH的对数产率比为-1.7。对9月13日至12月16日宽带R图像的监测显示，尘埃（A(0°)fρ）的产率在10月19日左右达到峰值，比12月8日的近日点过境早了50天。10月4日和27日的窄带图像显示，鲍里索夫彗发中的CN分布几乎对称，表明其向日半球甚至整个彗核都存在活动。我们的结果结合其他研究，揭示了其化学成分和随日心距变化的行为与我们观测到的其他任何彗星都不同。
英文摘要
We report on imaging, spectroscopy, and narrowband photometry of interstellar comet 2I/Borisov obtained at Lowell Observatory from 2019 September 13 to December 16. We measured chemical composition on four nights before perihelion, from October 4 to November 25 (2.466 to 2.028 au), with CN detections on all nights. Our measurements from October 27 represent the earliest reported detections of C$_2$ and C$_3$, where C$_2$-to-CN and C$_3$-to-CN log production rate ratios were $-$0.7 and $-$1.3, respectively. Both ratios increased by nearly 4$\times$ to $-$0.3 and $-$0.9 by November 25, an extremely large increase with heliocentric distance that is unprecedented in the Lowell Observatory comet database. We additionally observed OH and NH on November 25, with a derived H$_2$O production rate of 4.5$\times $10$^{26}$ mol s$^{-1}$ and very high log production rate ratios for CN-to-OH ($-$2.0) and NH-to-OH ($-$1.7). Monitoring from broadband $R$ images from September 13 to December 16 suggests dust ($A(0^{\circ})fρ$) production peaked around October 19, 50 days before its December 8 perihelion passage. Narrowband images from October 4 and 27 reveal a nearly symmetric CN distribution in Borisov's coma, suggesting activity over its entire sunward hemisphere and possibly its entire nucleus. Our results, combined with those from others, reveal a chemical composition and behavior with heliocentric distance unlike any other comet we have observed.
Comments26 pages, 7 figures, 5 tables. Accepted for publication in the Planetary Science Journal
