Photometry和彗星21 P/Giacobini-Zinner在2018年出现期间的高分辨率光谱学
Photometry and high-resolution spectroscopy of comet 21P/Giacobini-Zinner during its 2018 apparition
摘要：
本文报道了化学性质奇特的彗星族21 P/Giacobini-Zinner的测光和高分辨光谱学研究。彗星21 P是碳链耗尽家族的一个众所周知的成员，但也显示出胺的耗尽。我们用两台TRAPPIST望远镜（TN和TS）连续监测了七个多月的彗星，覆盖了从1.60 au入境到2.10 au出境的大日心距离范围，近日点在2018年9月10日的1.01 au。我们计算并跟踪了彗星轨道上尘埃（以Af $ρ$表示）和子种OH、NH、CN、C $_3$和C $_2$的气体产生率及其相对于OH和CN的丰度的演化。我们将它们与之前的显灵进行了比较。彗星的活动和产水率在2018年8月17日达到最大值（3.72 $\pm$ 0.07）$\times$ 10 $^{28}$ molec/s（r $_h$ =1.07 au），即近日点前24天。在红色滤光片中，A（0）f $ρ$的峰值在同一天达到（1646 $\pm$ 13）cm。在近日点前后，各种物种的丰度比在很大的日心距离范围内都是非常恒定的，这表明核表面的冰具有高度的均匀性。彗星的行为和活动水平在过去五个轨道上也非常相似。关于彗发尘埃的颜色，21 P显示出类似于JFC的反射梯度。在近日点后一周，我们在ESO VLT上用UVES获得了21 P的高分辨光谱。使用CN B-X（0，0）紫带，我们测量了$^{12}$ C/ $^{13}$ C和$^{14}$ N/ $^{15}$ N同位素比值，分别为100 $\pm$ 10和145 $\pm$ 10，两者都与通常在彗星中发现的非常一致。
英文摘要：
We report on photometry and high resolution spectroscopy of the chemically peculiar Jupiter-family Comet (hereafter JFC) 21P/Giacobini-Zinner. Comet 21P is a well known member of the carbon-chain depleted family but displays also a depletion of amines. We monitored continuously the comet over more than seven months with the two TRAPPIST telescopes (TN and TS), covering a large heliocentric distance range from 1.60 au inbound to 2.10 au outbound with a perihelion at 1.01 au on September 10, 2018. We computed and followed the evolution of the dust (represented by Af$ρ$) and gas production rates of the daughter species OH, NH, CN, C$_3$, and C$_2$ and their relative abundances to OH and to CN over the comet orbit. We compared them to those measured in the previous apparitions. The activity of the comet and its water production rate reached a maximum of (3.72$\pm$0.07)$\times$10$^{28}$ molec/s on August 17, 2018 (r$_h$=1.07 au), 24 days before perihelion. The peak value of A(0)f$ρ$ was reached on the same date (1646$\pm$13) cm in the red filter. The abundance ratios of the various species are remarkably constant over a large range of heliocentric distances, before and after perihelion, showing a high level of homogeneity of the ices in the surface of the nucleus. The behaviour and level of the activity of the comet is also remarkably similar over the last five orbits. About the coma dust colour, 21P shows reflectively gradients similar to JFCs. We obtained a high resolution spectrum of 21P with UVES at ESO VLT one week after perihelion. Using the CN B-X (0,0) violet band, we measured $^{12}$C/$^{13}$C and $^{14}$N/$^{15}$N isotopic ratios of 100$\pm$10 and 145$\pm$10, respectively, both in very good agreement with what is usually found in comets.
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