We present observations of the occultation of Umbriel by Oberon on 4 May, 2007. We believe this is the first observed mutual event between satellites of Uranus. Fitting a simple geometric model to the lightcurve, we measure the mid-event time with a precision of 4 seconds. We assume previously measured values for the albedos of the two satellites (Karkoschka 2001), and measure the impact parameter to be 500 +/- 80 km. These measurements are more precise than estimates based on current ephemerides for these satellites. Therefore observations of additional mutual events during the 2007-2008 Uranian equinox will provide improved estimates of their orbital and physical parameters.
@article{arxiv.0711.2095,
title = {An observation of a mutual event between two satellites of Uranus},
author = {M. G. Hidas and A. A. Christou and T. M. Brown},
journal= {arXiv preprint arXiv:0711.2095},
year = {2009}
}
Comments
4 pages, 3 figures, accepted for publication in MNRAS Letters