微弱的天王星不规则卫星Sycorax，Prospero，Stephano，Setebos和Trinculo的光曲线和颜色
Light curves and colours of the faint Uranian irregular satellites Sycorax, Prospero, Stephano, Setebos and Trinculo
摘要：
在Gladman等人（1998年）的工作之后，现在估计有许多不规则的卫星围绕天王星运行。尽管在过去的几年里进行了许多研究，但很少有人知道这些物体的光变曲线，并且不同作者得出的颜色之间存在不一致性。这种情况促使我们努力提高颜色和光曲线的知识。我们介绍并讨论了2005年7月29日至30日和2005年11月25日至30日夜间在ESO Paranal（智利）VLT进行的Sycorax、Prospero、Stephano、Setebos和Trinculo（天王星的五颗微弱不规则卫星）的时间序列观测。我们推导出西科拉斯和普洛斯彼罗的光变曲线以及所有这些天体的颜色。对于Sycorax，我们得到的颜色B-V =0.839 +/- 0.014，V-R = 0.531 +/- 0.005和光变曲线，这是一个周期性的变化，周期约为3.6小时，振幅约为0.067 +/- 0.004磁。我们得出的周期和颜色Sycorax是与我们以前的确定在1999年使用NTT。我们还得到了普洛斯彼罗的光变曲线，表明振幅约为0.2等，周期约为4小时。然而，我们的数据的稀疏性，阻止了光变曲线的更精确的表征，并且我们不能确定它们是单峰还是双峰。因此，这些周期和振幅必须被认为是初步估计。至于Setebos，Stephano和Trinculo，目前的数据不允许得出任何明确的周期性，尽管Setebos显示出与Prospero一样大的幅度的显着变化。普洛斯彼罗，Setebos，Stephano和Trinculo的颜色与文献的边缘一致。
英文摘要：
After the work of Gladman et al. (1998), it is now assessed that many irregular satellites are orbiting around Uranus. Despite many studies have been performed in past years, very few is know for the light-curves of these objects and inconsistencies are present between colours derived by different authors. This situation motivated our effort to improve both the knowledge of colours and light curves. We present and discuss time series observations of Sycorax, Prospero, Stephano, Setebos and Trinculo, five faint irregular satellites of Uranus, carried out at VLT, ESO Paranal (Chile) in the nights between 29 and 30 July, 2005 and 25 and 30 November, 2005. We derive light curves for Sycorax and Prospero and colours for all of these these bodies. For Sycorax we obtain colours B-V =0.839 +/- 0.014, V-R = 0.531 +/- 0.005 and a light curve which is suggestive of a periodical variation with period about 3.6 hours and amplitude about 0.067 +/- 0.004 mag. The periods and colours we derive for Sycorax are in agreement with our previous determination in 1999 using NTT. We derive also a light-curve for Prospero which suggests an amplitude of about 0.2 mag and a periodicity of about 4 hours. However, the sparseness of our data, prevents a more precise characterization of the light-curves, and we can not determine wether they are one-peaked or two-peaked. Hence, these periods and amplitudes have to be considered preliminary estimates. As for Setebos, Stephano and Trinculo the present data do not allow to derive any unambiguous periodicity, despite Setebos displays a significant variability with amplitude about as large as that of Prospero. Colours for Prospero, Setebos, Stephano and Trinculo are in marginal agreement with the literature.
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