彗星17P/Holmes 2007爆发：爆发物质的早期运动
The comet 17P/Holmes 2007 outburst: the early motion of the outburst material
摘要：
上下文2007年10月24日，周期彗星17 P/霍姆斯经历了一次惊人的爆发，在大约两天的时间里，它的视总亮度从V \sim 17增加到V \sim 2.5。我们报告的Wendelstein 0.8米望远镜（WST）测光观测的早期演化阶段的爆发。目标。我们研究了结构形态的演变，它的运动学，并估计了喷出的尘埃质量。方法.我们分析了2007年10月26日至2007年11月20日之间BVRI光度带中的126张图像。在所有的数据中，明亮的彗星核心与快速膨胀的尘埃云分离得很好，后者的大部分都包含在我们仪器的视野中。根据背景星被运动云遮蔽的差分测光，导出了喷出的尘埃质量。结果这两个核心以（9.87 +/-0.07）arcsec/day（0.135 +/-0.001 km/sec）的相对恒定速度相互远离。在尘埃云的内部区域，我们观察到其大小以平均恒定速度（14.6 +/-0.3）arcsec/day（0.200 +/-0.004 km/sec）线性增加。我们还发现了在膨胀云中存在径向速度梯度的证据，我们对膨胀彗发质量的估计是10 ^{-2}-1彗星质量的数量级，这意味着一个重要的解体事件。结论.我们解释了我们的意见的背景下，爆炸的情况下，这更可能是起源于一些内部不稳定的过程，而不是与小行星体的影响。由于这一事件的特殊性，有必要进行进一步的观察和调查，以揭示决定它的物理过程的性质。
英文摘要：
Context. On October 24, 2007 the periodic comet 17P/Holmes underwent an astonishing outburst that increased its apparent total brightness from magnitude V\sim17 up to V\sim2.5 in roughly two days. We report on Wendelstein 0.8 m telescope (WST) photometric observations of the early evolution stages of the outburst. Aims. We studied the evolution of the structure morphology, its kinematic, and estimated the ejected dust mass. Methods. We analized 126 images in the BVRI photometric bands spread between 26/10/2007 and 20/11/2007. The bright comet core appeared well separated from that one of a quickly expanding dust cloud in all the data, and the bulk of the latter was contained in the field of view of our instrument. The ejected dust mass was derived on the base of differential photometry on background stars occulted by the moving cloud. Results. The two cores were moving apart from each other at a relative projected constant velocity of (9.87 +/- 0.07) arcsec/day (0.135 +/-0.001 km/sec). In the inner regions of the dust cloud we observed a linear increase in size at a mean constant velocity of (14.6+/-0.3) arcsec/day (0.200+/-0.004 km/sec). Evidence of a radial velocity gradient in the expanding cloud was also found. Our estimate for the expanding coma's mass was of the order of 10^{-2}-1 comet's mass implying a significant disintegration event. Conclusions. We interpreted our observations in the context of an explosive scenario which was more probably originated by some internal instability processes, rather than an impact with an asteroidal body. Due to the peculiar characteristics of this event, further observations and investigations are necessary in order to enlight the nature of the physical processes that determined it.
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