Light curves of FBQS J0951+2635 in the r-band. Top panel: LT-NOT-MAO brightness records of both quasar images and the faint star S3. There is a gap of about 1000 d between the MAO monitoring campaign (before day 4000) and the LT-NOT follow-up observations starting in 2009. The records of B and S3 are offset by −0.70 and −1.35 mag, respectively. Bottom panel: DLC (black data points), where the data of the B image have been shifted by −16 d (time delay) and binned around the dates of the A image (using bins with a semisize of 4 d). We also show the single-epochmagnitude differences (grey data points), as well as the single-epoch flux ratio of the Mg II emission line in magnitudes (horizontal dashed line).