Multicolor photometry of the Uranus irregular satellites Sycorax and Caliban

We report on accurate BV RI photometry for the two Uranian irregular satell ites Sycorax and Caliban. We derive colors showing that Sycorax is bluer th an Caliban. Our data allow us to detect a significant variability in Caliba n's light curve, which suggests an estimated period of about 3 hr. Although it is the brighter of the two bodies, Sycorax does not display a strong, s tatistically significant variability. However, our data seem to suggest a p eriod of about 4 hr.