主带彗星P/2005 U1的物理性质
Physical Properties of Main-Belt Comet P/2005 U1 (Read)
摘要：
主带彗星动态占据主小行星带中的小行星轨道。在这里，我们提出的物理观测的第二个已知的成员，这一人口，P/2005 U1（读），这表明有力的彗星活动，从2005年10月24日至2005年12月27日。P/Read尘埃排放的Monte Carlo数值模拟表明，彗发和尾部的光学主导的尘埃颗粒大于10微米的大小与终端喷射速度为0.2至3米/秒。我们估计P/Read在此期间的质量损失率约为0.2 kg/s，大约比133 P/Elst-Pizarro的计算值大一个数量级。我们还发现，排放可能开始至少两个月前P/读取的发现，虽然我们注意到这是一个下限，更早的开始时间是可能的。在P/Read活跃时测得的光学颜色近似于太阳光（B-V=0.63+/-0.05，V-R=0.37+/-0.04，R-I=0.39+/-0.04），但很可能主要是彗发粒子。在2007年，当P/Read看起来很不活跃时，它的观测显示出一个非常小的核，绝对星等为H_R~20.1+/-0.4，对应的有效半径为r~0.3 km。P/Read的活动与升华驱动的尘埃排放是一致的，但与撞击引起的尘埃排放不一致，尽管2005年爆发的异常强度表明它可能是由于新暴露的挥发性物质的升华。
英文摘要：
The main-belt comets occupy dynamically asteroidal orbits in the main asteroid belt. Here we present physical observations of the second-known member of this population, P/2005 U1 (Read), which showed vigorous cometary activity from 2005 October 24 to 2005 December 27. Monte Carlo numerical simulations of P/Read's dust emission indicate that the coma and tail are optically dominated by dust particles larger than 10 microns in size with terminal ejection velocities of 0.2 to 3 m/s. We estimate P/Read's mass loss rate during this period to be approximately 0.2 kg/s, roughly an order of magnitude larger than that calculated for 133P/Elst-Pizarro. We also find that emission likely began at least two months prior to P/Read's discovery, though we note this is a lower limit and that earlier start times are possible. Optical colors measured for P/Read while it was active are approximately solar (B-V=0.63+/-0.05, V-R=0.37+/-0.04, R-I=0.39+/-0.04) but are likely to be dominated by coma particles. Observations of P/Read in 2007 when it appears largely inactive show an extremely small nucleus with an absolute magnitude of H_R~20.1+/-0.4, corresponding to an effective radius of r~0.3 km. P/Read's activity is consistent with sublimation-driven dust emission and inconsistent with dust emission due to an impact, though the unusual strength of the 2005 outburst suggests the possibility that it could have been due to the sublimation of a freshly-exposed reservoir of volatile material.
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