Consequences of a possible jet-star interaction in the inner central parsec of Centaurus A

TL;DR

This study uses high-resolution VLBI observations over 3.5 years to analyze the inner parsec of Centaurus A's jet, revealing complex dynamics and evidence of jet-star interaction with potential implications for high-energy emissions.

Contribution

First detailed kinematic analysis of Centaurus A's inner jet with evidence of jet-star interaction affecting jet structure and emission.

Findings

Detection of a persistent brightness minimum indicating a jet-star interaction

Observation of complex spine-sheath jet structure with downstream acceleration

Implications for neutrino and high-energy emission from jet interactions

Abstract

The jet-counterjet system of the closest radio-loud active galaxy Centaurus A (Cen A) can be studied with Very Long Baseline Interferometry (VLBI) on unprecedented small linear scales of ~0.018pc. These high-resolution observations provide essential information on jet emission and propagation within the inner parsec of an AGN jet. We present the results of a kinematic study performed within the framework of the Southern-hemisphere AGN monitoring program TANAMI. Over 3.5years, the evolution of the central-parsec jet structure of Cen A was monitored with VLBI. These observations reveal complex jet dynamics which are well explained by a spine-sheath structure supported by the downstream acceleration occurring where the jet becomes optically thin. Both moving and stationary jet features are tracked. A persistent local minimum in surface brightness suggests the presence of an obstacle interrupting the jet flow, which can be explained by the interaction of the jet with a star at a distance of ~0.4pc from the central black hole. We briefly discuss possible implications of such an interaction regarding the expected neutrino and high-energy emission and the effect on a putative planet.