BROAD ABSORPTION-LINE TIME VARIABILITY IN THE QSO CSO-203

We present spectroscopy of the BALQSO CSO 203 during four epochs over a 17 month time span. These data show three distinct levels in the broad absorption lines (BALs) of Si IV lambda-1397 and C IV lambda-1549. We also note possible variations in the N v lambda-1240 and Al III lambda-1857 absorption troughs. A broad-band monitoring effort during this period shows that the continuum level remained constant to within 10%. We argue that the triggering mechanism for the absorption-line changes is most likely synchronous with the continuum source photons; however, no correlation with the central source has yet been found. The observed variations are consistent with changes in the ionization level in the broad absorption-line region (BALR). We discuss possible mechanisms for these changes and the implications for the structure of the BALR.