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

TL;DR

This study used multi-epoch VLBI observations to monitor the jet activity of 3C 84 during its 2005 outburst, revealing a new component with measurable motion and providing insights into jet dynamics during gamma-ray activity.

Contribution

First measurement of sub-pc jet kinematics in 3C 84 during a gamma-ray active phase using multi-epoch VLBI observations.

Findings

Confirmed association of outburst with central ~1 pc core.

Detected a new jet component with brightness increase in 2008.

Measured the new component's projected speed at 0.23c and a ~40° change in movement direction.

Abstract

Multi-epoch Very Long Baseline Interferometry (VLBI) study of the sub-pc scale jet of 3C 84 is presented. We carried out 14-epoch VLBI observations during 2006-2009 with the Japanese VLBI Network (JVN) and the VLBI Exploration of Radio Astrometry (VERA), immediately following the radio outburst that began in 2005. We confirmed that the outburst was associated with the central ~1 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 the 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 is 0.23c 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 ~40 degree. This is the first measurement of kinematics of a sub-pc jet in a gamma-ray active phase. Possible detection of jet deceleration and the jet kinematics in connection with the gamma-ray emission is discussed.