Periodic morphological changes in gamma-ray binaries

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.