Context : A stellar occultation observed on 3rd June 2013 revealed the presence of two dense and narrow rings separated by a small gap around the Centaur object ( 10199 ) Chariklo .
The composition of these rings is not known .
We suspect that water ice is present in the rings , as is the case for Saturn and other rings around the giant planets .

Aims : In this work , we aim to determine if the variability in the absolute magnitude of Chariklo and the temporal variation of the spectral ice feature , even when it disappeared in 2007 , can be explained by an icy ring system whose aspect angle changes with time .

Methods : We explained the variations on the absolute magnitude of Chariklo and its ring by modeling the light reflected by a system as the one described above .
Using X-Shooter at VLT , we obtained a new reflectance spectra .
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 light scattering to fit the visible and near-infrared spectra that shows different characteristics to obtain information on the composition of Chariklo and its rings .

Results : We showed that 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 \pm 0.5 , \delta = 41.48 \pm 0.2 ^ { o } ( \lambda = 137.9 \pm 0.5 , \beta = 27.7 \pm 0.2 ^ { 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 , we derived the composition of the Chariklo surface and that of the rings using the result on the pole solution .
Chariklo surface is composed with about 60 % of amorphous carbon , 30 % of silicates and 10 % of organics ; no water ice was found on the surface .
The ring , on the other hand , contains 20 % of water ice , 40-70 % of silicates , and 10-30 % of tholins and small quantities of amorphous carbon .

Conclusions :