Phenomenology of gamma-ray emitting binaries

TL;DR

Gamma-ray emitting binaries are complex astrophysical systems that are actively studied for their unique observational properties and potential contribution to cosmic rays, with ongoing debates about their characteristics.

Contribution

This paper reviews current observational results and discusses controversial properties of gamma-ray emitting binaries, highlighting recent advances in understanding these systems.

Findings

GREBs exhibit diverse multi-wavelength emissions.

Long-term monitoring reveals exceptions to typical behaviors.

GREBs may significantly contribute to Galactic cosmic rays.

Abstract

Gamma-ray emitting binaries (GREBs) are complex systems. Its study became in the last years a major endeavour for the high-energy astrophysics community, both from an observational and a theoretical perspective. Whereas the accumulation of observation time for most Galactic gamma-ray sources is typically leading to highly accurate descriptions of their steady phenomenology, GREBs keep providing "exceptions to the rule" either through long-term monitoring of known systems or in the discovery of new sources of this class. Moreover, many GREBs have been identified as powerful radio, optical and X-ray emitters, and may significantly contribute as well to the Galactic cosmic-ray sea. Their understanding implies, therefore, solving a puzzle in a broad-band and multi-messenger context. In these proceedings we will summarise our current understanding of GREBs, emphasising the most relevant observational results and reviewing a number of controversial properties.