Si II doublet in Visit B_fuv with the lines centered on their rest wavelengths (vertical dotted lines). The first exposure (blue) shows a flux decrease compared tothe average of the other spectra in the visit (black), consistent with absorption from an optically thin cloud of silicon gas. The green (before convolution) and red (after convolution) profiles correspond to a best-fit model for the intrinsic stellar line (solid line) and the occulting cloud (dashed line).