VLBI Monitoring of 3C 84 (NGC 1275) in Early Phase of the 2005 Outburst

Abstract

Abstract Multi-epoch Very Long Baseline Interferometry (VLBI) study of a sub-pc scale jet of 3C 84 is presented. We carried out 14-epoch VLBI observations during 2006–2009 with the Japanese VLBI Network and the VLBI Exploration of Radio Astrometry, immediately following a radio outburst that began in 2005. We confirmed that the outburst was associated with the central $\sim1$ pc core, accompanying the emergence of a new component. This is striking evidence of the recurrence of jet activity. The new component became brighter during 2008, in contrast to constant $\gamma$-ray emission that was observed with the Fermi Gamma-ray Space Telescope during the same time. We found that the projected speed of the new component was 0.23$ c$ from 2007/297 (2007 October 24) to 2009/114 (2009 April 24). The direction of movement of this component differs from that of the pre-existing component by $\sim $40$^{\circ}$. This was the first measurement of the kinematics of a sub-pc jet in a $\gamma$-ray active phase. A possible detection of jet deceleration and the jet kinematics in connection with the $\gamma$-ray emission is discussed.