Core-shift vectors and core-shift power-law fit for IIIZw2. (a) Weighted mean core-shift vectors and mean direction vector of IIIZw 2 combining all calibrators. (b) Projected core-shift values with K band as the reference frequency using the weighted mean core-shift vectors of Table 4. The values relative to K band are 0.089 ± 0.081 mas for CK, −0.025 ± 0.040 mas for XK, and −0.026 ± 0.027 mas for UK.