2017年12月半人马座174 P/Echeclus爆发的物理特征
Physical Characterization of the December 2017 Outburst of the Centaur 174P/Echeclus
摘要：
半人马座是介于活跃的内太阳系木星家族彗星和外海王星区域不活跃的祖先之间的小太阳系天体。在半人马座中，174 P/Echeclus以其2005年的大规模爆发而闻名，其中一个大的明显活跃的碎片从主核喷射出超过逃逸速度。我们在Faulkes南北望远镜和NASA IRTF拍摄的2017年12月爆发后的第一周内展示了Echeclus的可见光成像和近红外光谱，这是自2005年以来最大的爆发。彗发被认为是高度不对称的。在近红外2D光谱中看到了第二个峰，这在可见光图像中得到了强烈的暗示，相对于原子核呈双曲线移动。检索Echelcus的反射光谱是一致的，未被掩盖的核，但变得更蓝时，使用更宽的提取孔径。我们发现，Echeclus的昏迷是最好的解释为占主导地位的大蓝色尘埃颗粒，这与以前的工作。我们还对Echeclus最近的演化进行了高分辨率的轨道整合，没有发现可以驱动其现代演化的大的轨道变化。我们将可见光和近红外数据集中的第二个峰值解释为爆发时喷出的大于尘埃的碎片的大云。如果Echeclus是典型的半人马座，那么在其他半人马座上每年可能会有几次碎片喷射或碎片化事件被忽视。
英文摘要：
The Centaurs are the small solar system bodies intermediate between the active inner solar system Jupiter Family Comets and their inactive progenitors in the trans-Neptunian region. Among the fraction of Centaurs which show comet-like activity, 174P/Echeclus is best known for its massive 2005 outburst in which a large apparently active fragment was ejected above the escape velocity from the primary nucleus. We present visible imaging and near-infrared spectroscopy of Echeclus during the first week after its December 2017 outburst taken at the Faulkes North & South Telescopes and the NASA IRTF, the largest outburst since 2005. The coma was seen to be highly asymmetric. A secondary peak was seen in the near-infrared 2D spectra, which is strongly hinted at in the visible images, moving hyperbolically with respect to the nucleus. The retrieved reflectance spectrum of Echelcus is consistent with the unobscured nucleus but becomes bluer when a wider extraction aperture is used. We find that Echeclus's coma is best explained as dominated by large blue dust grains, which agrees with previous work. We also conducted a high-resolution orbital integration of Echeclus's recent evolution and found no large orbital changes that could drive its modern evolution. We interpret the second peak in the visible and near-infrared datasets as a large cloud of larger-than-dust debris ejected at the time of outburst. If Echeclus is typical of the Centaurs, there may be several debris ejection or fragmentation events per year on other Centaurs that are going unnoticed.
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