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 spectroscop
y 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), wh
ereas the reflectivity strongly decreases beyond 1 mum and is rather at ove
r the near-infrared range. We were not able to reproduce the spectral behav
iour of Sycorax using simple materials. A rotational effect is suggested to
explain the shape of the spectrum. BVRIJ magnitudes have been measured ove
r 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 measurem
ents and the J measurement (30 min later) could explain the shape of the sp
ectrum, but further investigation is required to conclude.