Photometric and spectroscopic observations of Sycorax, satellite of Uranus^*

¹ Observatoire de Paris, Meudon, France
² ESO, Chile
³ IAS, Orsay, France
⁴ Lab. de Planétologie de Grenoble, St Martin d'Hères, France

Corresponding author: J. Romon, jennifer.romon@obspm.fr

Received: 9 May 2001
Accepted: 26 June 2001

Abstract

Sycorax is the brightest of the five irregular Uranian satellites recently discovered. These satellites are supposed to be captured bodies. We present visible and near-infrared photometry, as well as near-infrared spectroscopy of Sycorax. The overall shape of the spectrum is quite puzzling: it has a red slope in the visible (such as Centaurs and Transneptunian objects), whereas the reflectivity strongly decreases beyond 1 μm and is rather flat over the near-infrared range. We were not able to reproduce the spectral behaviour of Sycorax using simple materials. A rotational effect is suggested to explain the shape of the spectrum. BVRIJ magnitudes have been measured over a period of 1 hour, with five V measurements which do not show any strong variation. So only a strong change in the magnitude between the V measurements and the J measurement (30 min later) could explain the shape of the spectrum, but further investigation is required to conclude.