Epoch 13, 2008 January 03. (a) Core spectrum, Cb possibly represents the core. (b) Core-shift vectors of all frequency pairs. (c) Power-law fit is shown with the red curve. Due to the poor (u, v) coverage, the core at the C band cannot be well resolved, producing ambiguities on its location. As a result, very large core-shift values above 1 mas were measured. This observation was not included in the variability analysis.