伽利略卫星对J5 Amalthea日食的观测探测
Observational detection of eclipses of J5 Amalthea by the Galilean satellites
摘要：
我们进行了观测的小木星卫星Amalthea（J5），因为它是由伽利略卫星在2009年的木星春分点附近的日食，以应用相互事件测光技术的天体测量确定这颗卫星的位置。这些观测是在2009年6月至2009年9月期间从夏威夷毛伊岛和澳大利亚赛丁泉岛分别用2米福克斯望远镜南北进行的。我们使用PanStarrs-Z滤光片在光谱的近红外部分进行观察，木星靠近视场边缘，以减轻来自行星的眩光。在使用最近的JPL卫星星历预测的日食时间期间，以>1/min的速率获取帧。从这些帧中减去天空背景后，对Amalthea和附近的一颗恒星进行了差分孔径测光。我们已经获得了三条光变曲线，显示出阿玛尔泰亚的光通量明显下降，表明日食正如预测的那样发生了。对这些数据进行模型拟合，以得出最大通量下降时间和碰撞参量的最佳估计值。这与阿马尔泰亚的星历表一致，但表明阿马尔泰亚比其预测的位置稍微提前，并且比其预测的位置更接近木星，在这些方向上的星历表不确定性约为一半。我们认为，在2014-15年的下一个日食季节，一个更高节奏的测光精确度在5%或更好的地面运动应该产生的位置在0”.5和影响相应的改善Amalthea的星历。
英文摘要：
We carried out observations of the small jovian satellite Amalthea (J5) as it was being eclipsed by the Galilean satellites near the 2009 equinox of Jupiter in order to apply the technique of mutual event photometry to the astrometric determination of this satellite's position. The observations were carried out during the period 06/2009-09/2009 from the island of Maui, Hawaii and Siding Spring, Australia with the 2m Faulkes Telescopes North and South respectively. We observed in the near-infrared part of the spectrum using a PanStarrs-Z filter with Jupiter near the edge of the field in order to mitigate against the glare from the planet. Frames were acquired at rates >1/min during eclipse times predicted using recent JPL ephemerides for the satellites. Following subtraction of the sky background from these frames, differential aperture photometry was carried out on Amalthea and a nearby field star. We have obtained three lightcurves which show a clear drop in the flux from Amalthea, indicating that an eclipse took place as predicted. These were model-fitted to yield best estimates of the time of maximum flux drop and the impact parameter. These are consistent with Amalthea's ephemeris but indicate that Amalthea is slightly ahead of, and closer to Jupiter than, its predicted position by approximately half the ephemeris uncertainty in these directions. We argue that a ground-based campaign of higher-cadence photometry accurate at the 5% level or better during the next season of eclipses in 2014-15 should yield positions to within 0".5 and affect a corresponding improvement in Amalthea's ephemeris.
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