Marchis F, Kaasalainen M, Hom E F Y, Berthier J, Enriquez J, Hestroffer D, Le Mignant D, de Pater I
Department of Astronomy, University of California, 601 Campbell Hall, Berkeley, CA 94720-3411, USA.
Icarus. 2006 Nov;185(1):39-63. doi: 10.1016/j.icarus.2006.06.001.
This paper presents results from a high spatial resolution survey of 33 main-belt asteroids with diameters >40 km using the Keck II Adaptive Optics (AO) facility. Five of these (45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra) were confirmed to have satellite. Assuming the same albedo as the primary, these moonlets are relatively small (∼5% of the primary size) suggesting that they are fragments captured after a disruptive collision of a parent body or captured ejecta due to an impact. For each asteroid, we have estimated the minimum size of a moonlet that can positively detected within the Hill sphere of the system by estimating and modeling a 2-σ detection profile: in average on the data set, a moonlet located at 2/100 × R(Hill) (1/4 × R(Hill)) with a diameter larger than 6 km (4 km) would have been unambiguously seen. The apparent size and shape of each asteroid was estimated after deconvolution using a new algorithm called AIDA. The mean diameter for the majority of asteroids is in good agreement with IRAS radiometric measurements, though for asteroids with a D < 200 km, it is underestimated on average by 6-8%. Most asteroids had a size ratio that was very close to those determined by lightcurve measurements. One observation of 104 Klymene suggests it has a bifurcated shape. The bi-lobed shape of 121 Hermione described in Marchis et al. [Marchis, F., Hestroffer, D., Descamps, P., Berthier, J., Laver, C., de Pater, I., 2005c. Icarus 178, 450-464] was confirmed after deconvolution. The ratio of contact binaries in our survey, which is limited to asteroids larger than 40 km, is surprisingly high (∼6%), suggesting that a non-single configuration is common in the main-belt. Several asteroids have been analyzed with lightcurve inversions. We compared lightcurve inversion models for plane-of-sky predictions with the observed images (9 Metis, 52 Europa, 87 Sylvia, 130 Elektra, 192 Nausikaa, and 423 Diotima, 511 Davida). The AO images allowed us to determine a unique photometric mirror pole solution, which is normally ambiguous for asteroids moving close to the plane of the ecliptic (e.g., 192 Nausikaa and 52 Europa). The photometric inversion models agree well with the AO images, thus confirming the validity of both the lightcurve inversion method and the AO image reduction technique.
本文展示了使用凯克二号自适应光学（AO）设备对33颗直径大于40千米的主带小行星进行高空间分辨率观测的结果。其中五颗小行星（45欧仁妮娅、87西尔维亚、107卡米拉、121赫敏、130厄勒克特拉）被确认有卫星。假设卫星与主星反照率相同，这些小卫星相对较小（约为主星大小的5%），这表明它们是母体发生破裂碰撞后捕获的碎片，或者是因撞击而捕获的抛射物。对于每颗小行星，我们通过估计和模拟2-σ探测剖面，估算了在系统的希尔球内能够被明确探测到的小卫星的最小尺寸：在数据集中平均而言，位于2/100×R（希尔）（1/4×R（希尔））处、直径大于6千米（4千米）的小卫星能够被清晰观测到。使用一种名为AIDA的新算法进行去卷积后，估算了每颗小行星的视尺寸和形状。大多数小行星的平均直径与红外天文卫星（IRAS）的辐射测量结果吻合良好，不过对于直径D<200千米的小行星，平均低估了6-8%。大多数小行星的尺寸比与光变曲线测量结果非常接近。对104克利墨涅的一次观测表明它具有分叉形状。马尔基斯等人[马尔基斯，F.，埃斯特罗费尔，D.，德康普斯，P.，贝蒂埃，J.，拉弗，C.，德帕特，I.，2005c。《伊卡鲁斯》178，450-464]描述的121赫敏的双叶形状在去卷积后得到了确认。我们的调查仅限于直径大于40千米的小行星，其中接触双星的比例出奇地高（约6%），这表明非单一构型在主带中很常见。对几颗小行星进行了光变曲线反演分析。我们将用于预测天空平面的光变曲线反演模型与观测图像（9号墨提斯、52号欧罗巴、87号西尔维亚、130号厄勒克特拉、192号瑙西卡、423号狄俄蒂玛、511号达维达）进行了比较。AO图像使我们能够确定一个独特的光度学镜面极点解，对于靠近黄道面运行的小行星（例如192号瑙西卡和52号欧罗巴），这通常是不明确的。光度反演模型与AO图像吻合良好，从而证实了光变曲线反演方法和AO图像还原技术的有效性。
