We present observations of HCO+ 1–0 absorption lines toward two extragalactic compact radio sources, NRAO 150 and BL Lac with the Korean VLBI Network in order to investigate their time variation over 20 years by Galactic foreground clouds. It is found that the line shape of –17 km s−1 component changed marginally during 1993–1998 period and has remained unaltered thereafter for NRAO 150. Its behavior is different from that of H2CO 110–111, suggesting chemical differentiation on ∼ 20 AU scale, the smallest ever seen. On the other hand, BL Lac exhibits little temporal variation for the HCO+ and H2CO lines. Our observation also suggests that Korea VLBI Network performs reliably in the spectrum mode in that the shapes of the new HCO+ 1–0 spectra are in good agreement with the previous ones to an accuracy of a few percent except the time varying component toward NRAO 150.

We present a kinematic study of the parsec-scale radio jet in OJ 287, one of the most studied BL Lac objects, during γ-ray ares, to explore the relation between parsec-scale radio jet activity and γ-ray emission. The 22-GHz light curve of OJ 287 show three obvious are events around 2011 May, 2011 October, and 2012 March. The second radio are occurred during the γ-ray aring period, and the third radio are seemed to precede the γ-ray are by one month. One jet component moved outward with respect to the core component with an apparent superluminal speed (~ 11c) from 2010 November to 2011 November. Then it changed direction, moving apparently inward in 2011 November, when the γ-ray are occurred. The observed apparent inward motion of the jet at 22 GHz could be caused by a new jet component, unresolved at 22 GHz, in the innermost region.