  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.
