C/2020 F3（NEOWISE）从SOHO/SWAN到其活性外观的产水速率
Water Production Rate of C/2020 F3 (NEOWISE) from SOHO/SWAN over Its Active Apparition
摘要：
C/2020 F3（NEOWISE）是在2020年3月27日拍摄的宽视场红外巡天探测器（NEOWISE）的近地天体计划图像中发现的，并已成为2020年的大彗星。太阳和日光层观测站（SOHO）航天器上的太阳风各向异性（SWAN）相机位于地球-太阳L1拉格朗日点周围的光环轨道上，每天拍摄氢莱曼α的全天空图像。水的产生率是根据2020年7月3日在彗星近日点两侧测量的4个月时间内的SWAN氢莱曼α亮度和彗星的空间分布确定的。以s^-1为单位的产水率在近日点附近具有适度的不对称性，并随日心距r的变化而变化，以au为单位的产水率在近日点前后分别为（6.9+/-0.5）x 10^28 r^-2.5+/-0.2和（10.1+/-0.5）x 10^28 r^-3.5+/-0.1。这与彗星在之前的一次或多次显灵中穿过太阳系的行星区域是一致的。在近日点后不久，当彗星位于天鹅座星系的避日区之外时，即彗星距离太阳0.324天文单位时，测得的水的产生速率高达5.27 x 10^30 s^-1。
英文摘要：
C/2020 F3 (NEOWISE) was discovered in images from the Near Earth Object program of the Wide-Field Infrared Survey Explorer (NEOWISE) taken on 27 March 2020 and has become the Great Comet of 2020. The Solar Wind ANisotropies (SWAN) camera on the Solar and Heliospheric Observatory (SOHO) spacecraft, located in a halo orbit around the Earth-Sun L1 Lagrange point, makes daily full-sky images of hydrogen Lyman-alpha. Water production rates were determined from the SWAN hydrogen Lyman-alpha brightness and spatial distribution of the comet measured over a 4-month period of time on either side of the comet's perihelion on 3 July 2020. The water production rate in s^-1 was moderately asymmetric around perihelion and varied with the heliocentric distance, r, in au as (6.9+/-0.5) x 10^28 r^-2.5+/-0.2 and (10.1+/-0.5) x 10^28 r^-3.5+/-0.1 before and after perihelion, respectively. This is consistent with the comet having been through the planetary region of the solar system on one or more previous apparitions. A water production rates as large as 5.27 x 10^30 s^-1 were determined shortly after perihelion, once the comet was outside the solar avoidance area of SWAN, when the comet was 0.324 au from the Sun.
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