  In this work we aim to study if the variability in the absolute magnitude of
Chariklo and the temporal variation of the spectral ice feature, even its
disappearance in 2007, can be explained by an icy ring system whose aspect
angle changes with time. We modeled the light reflected by a system as the one
described above to explain the variations on the absolute magnitude of Chariklo
and its rings. Using X-Shooter at VLT we obtained a new reflectance spectra,
here we compared this new set of data with the ones available in the
literature. We showed how the water ice feature is visible in 2013 in
accordance with the ring configuration, which had an opening angle of nearly
34$^o$ in 2013. Finally we also used models of the scattering of light to fit
the visible and near-infrared spectra showing different characteristic to
obtain information on the composition of Chariklo and its rings. {We showed
that past absolute photometry of Chariklo from the literature and new
photometric data that we obtained in 2013 can be explained by a ring of
particles whose opening angle changes as a function of time. We used the two
possible pole solutions for the ring system and found that only one of them,
$\alpha$=151.30$\pm0.5$, $\delta=41.48\pm0.2$ $^o$ ($\lambda=137.9\pm0.5$,
$\beta=27.7\pm0.2$ $^o$) provides the right variation of the aspect angle with
time to explain the photometry, whereas the other possible pole solution fails
to explain the photometry. From spectral modeling, using the result on the pole
solution, we derived the composition of Chariklo surface and of that of the
rings. Chariklo surface is composed by nearly 60% of amorphous carbon, 30% of
silicates and 10\% of organics, no water ice was found on the surface. Whereas
the ring contains 20% of water ice, 40-70% of silicates and 10-30% of tholins
and small quantities of amorphous carbon.
