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标题：Physical Characterization of Interstellar Comet 2I/2019 Q4 (Borisov)
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作者：Man-To Hui (許文韜) ; Quan-Zhi Ye (葉泉志) ; Dora Föhring 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2020
卷号：160
期号：2
页码：1-12
DOI：10.3847/1538-3881/ab9df8
语种：English
出版社：American Institute of Physics
摘要：We present a study of interstellar comet 2I/2019 Q4(Borisov) using both preperihelion and postperihelionobservations spanning late September 2019 through late January 2020. The intrinsic brightness of the comet wasobserved to continuously decline throughout the timespan, likely due to the decreasing effective scattering cross-section as a result of volatile sublimation with a slope of -0.43土0.02km' d '. We witnessed no significant changein the slightly reddish color of the comet, with mean values of(g -r)= 0.68±0.04,(r -) =0.23± 0.03, andthe normalized reflectivity gradient across the g and i bands S(g, i) =(10.6± 1.4)% per 10‘A, all unremarkable inthe context of solar system comets. Using the available astrometric observations, we confidently detect thenongravitational acceleration of the comet following a shallow heliocentric distance dependence of 'H:Accordingly, we estimate that the nucleus is most likely≤0.4 km in radius, and that a fraction of ≥0.2% of the totalmass of the nucleus has been eroded due to the sublimation activity since the earliest observation of the comet in 2018December by the time of perihelion.Our morphology simulation suggests that the dust ejection speed increased from～4 ms ' in 2019 September to J7ms ' around perihelion for the optically dominant dust grains with 3～ 0.01,and that the observable dust grains are no smaller than micron size.