Periodic morphological changes in gamma-ray binaries

TL;DR

This paper reviews VLBI observations of gamma-ray binaries, highlighting their periodic morphological changes and the repeatability of radio structures aligned with their orbital motions.

Contribution

It provides new VLBI observations demonstrating the periodic morphological changes in gamma-ray binaries and confirms the repeatability of their radio structures.

Findings

Radio structures are repeatable with the orbital period.

VLBI imaging reveals morphological changes correlated with orbital phases.

Observations support models of particle acceleration and gamma-ray emission in these systems.

Abstract

Gamma-ray binaries allow us to study physical processes such as particle acceleration up to very-high energies and gamma-ray emission and absorption with changing geometrical configurations on a periodic basis. They produce outflows of radio-emitting particles whose structure can be imaged with Very Long Baseline Interferometry (VLBI). We present recent and new VLBI observations of PSR B1259-63, LS 5039, LS I +61 303, and HESS J0632+057. For the first three cases the results show the repeatability of their radio structures with the orbit of the binary system.