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arXiv 1605.01705astro-ph.EP
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极低活动彗星209 P/ LINEAR在2014年非常接近期间

The Extremely Low Activity Comet 209P/LINEAR During Its Extraordinary Close Approach in 2014

David G. Schleicher, Matthew M. Knight

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22 pages, including 4 figures
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摘要：

我们在2014年5月期间对209 P/LINEAR彗星进行了非常接近地球的观测活动，这是两个世纪以来第三个最小的近地点。这些情况使我们能够对这个本质上暗淡的物体进行几项研究，包括测量气体和尘埃的产生率，寻找彗发形态，以及直接探测核以测量其性质。事实上，我们成功地测量了35年来完整彗星的最低产水率和相应的最小活动面积，约为0.007平方公里。当结合雷达发现的核尺寸（Howell et al. 2014）时，这也产生了任何彗星的最小活动分数，约为0.024%。总之，这强烈地表明209 P/LINEAR正在成为一个惰性物体。探测到了彗核，但由于观测到的变化和变化的空间尺度，很难从彗发内部分离出来。即便如此，我们还是能够测量到一个双峰光变曲线，与Hergenrother（2014）发现的两个可行旋转周期中较短的一个相一致。尘埃彗发的径向轮廓非常陡峭，与其他一些非常贫血的彗星相似，并暗示存在蒸发的冰粒。

英文摘要：

We present results from our observing campaign of Comet 209P/LINEAR during its exceptionally close approach to Earth during May of 2014, the third smallest perigee of any comet in two centuries. These circumstances permitted us to pursue several studies of this intrinsically faint object, including measurements of gas and dust production rates, searching for coma morphology, and direct detection of the nucleus to measure its properties. Indeed, we successfully measured the lowest water production rates of an intact comet in over 35 years and a corresponding smallest active area, ~0.007 km^2. When combined with the nucleus size found from radar (Howell et al. 2014), this also yields the smallest active fraction for any comet, ~0.024%. In all, this strongly suggests that 209P/LINEAR is on its way to becoming an inert object. The nucleus was detected but could not easily be disentangled from the inner coma due to seeing variations and changing spatial scales. Even so, we were able to measure a double-peaked lightcurve consistent with the shorter of two viable rotational periods found by Hergenrother (2014). Radial profiles of the dust coma are quite steep, similar to that observed for some other very anemic comets and suggestive that vaporizing icy grains are present.

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