Proper motion and apparent contraction in J0650+6001

TL;DR

This study uses multi-epoch VLBI observations to analyze the kinematics of the compact radio source J0650+6001, revealing apparent contraction and expansion that inform jet dynamics and orientation.

Contribution

It provides the first detailed multi-epoch VLBI analysis of J0650+6001, demonstrating apparent contraction and expansion, and models jet velocities and orientation with Doppler beaming effects.

Findings

Apparent separation velocity of outer components is 0.39c.

Apparent contraction velocity of central components is 0.37c.

Jet intrinsic velocity estimated at 0.43c with a 12-28 degree angle to line of sight.

Abstract

We present a multi-epoch and multi-frequency VLBI study of the compact radio source J0650+6001. In VLBI images the source is resolved into three components. The central component shows a flat spectrum, suggesting the presence of the core, while the two outer regions, with a steeper spectral index, display a highly asymmetric flux density. The time baseline of the observations considered to derive the source expansion covers about 15 years. During this time interval, the distance between the two outer components has increased by 0.28+/-0.13 mas, that corresponds to an apparent separation velocity of 0.39c+/-0.18c and a kinematic age of 360+/-170 years. On the other hand, a multi-epoch monitoring of the separation between the central and the southern components points out an apparent contraction of about 0.29+/-0.02 mas, corresponding to an apparent contraction velocity of 0.37c+/-0.02c. Assuming that the radio structure is intrinsically symmetric, the high flux density ratio between the outer components can be explained in terms of Doppler beaming effects where the mildly relativistic jets are separating with an intrinsic velocity of 0.43c+/-0.04c at an angle between 12 and 28 degrees to the line of sight. In this context, the apparent contraction may be interpreted as a knot in the jet that is moving towards the southern component with an intrinsic velocity of 0.66c+/-0.03c, and its flux density is boosted by a Doppler factor of 2.0.