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arXiv 1606.07421astro-ph.EP
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近地小行星的反照率分布

The Albedo Distribution of Near Earth Asteroids

Edward L. Wright, Amy Mainzer, Joseph Masiero, Tommy Grav, James Bauer

摘要:

2010年的低温WISE任务对小行星极为敏感,对探测暗天体没有偏见。WISE在全低温任务期间观测到的428颗近地小行星(NEAs)的轨道可以用两个Rayleigh分布之和的三参数函数很好地拟合。对于负值,瑞利分布为零,对于正值x,瑞利分布遵循$f(x) = x \exp[-x^2/(2σ^2)]/σ^2$。峰值在x=σ处,因此位置和宽度是联系在一起的。这三个参数是暗总体中的对象的分数、暗峰的位置和较亮峰的位置。我们发现,25.3%的小行星观测到的WISE是在一个非常黑暗的人口在$p_V = 0.03$峰值,而其他74.7%的小行星观测到的WISE是在一个中等黑暗的人口峰值在$p_V = 0.168$。这种双峰分布的一个后果是,国会要求找到90%的直径大于140米的近地小行星,而测量到H=22等则无法满足这一要求,因为一颗直径为140米的小行星在非常暗的峰值处的H=23.7等,而超过10%的近地小行星的暗度超过p_V = 0.03。

英文摘要:

The cryogenic WISE mission in 2010 was extremely sensitive to asteroids and not biased against detecting dark objects. The albedos of 428 Near Earth Asteroids (NEAs) observed by WISE during its fully cryogenic mission can be fit quite well by a 3 parameter function that is the sum of two Rayleigh distributions. The Rayleigh distribution is zero for negative values, and follows $f(x) = x \exp[-x^2/(2σ^2)]/σ^2$ for positive x. The peak value is at x=σ, so the position and width are tied together. The three parameters are the fraction of the objects in the dark population, the position of the dark peak, and the position of the brighter peak. We find that 25.3% of the NEAs observed by WISE are in a very dark population peaking at $p_V = 0.03$, while the other 74.7% of the NEAs seen by WISE are in a moderately dark population peaking at $p_V = 0.168$. A consequence of this bimodal distribution is that the Congressional mandate to find 90% of all NEAs larger than 140 m diameter cannot be satisfied by surveying to H=22 mag, since a 140 m diameter asteroid at the very dark peak has H=23.7 mag, and more than 10% of NEAs are darker than p_V = 0.03.

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