Microquasars as the major contributors to Galactic cosmic rays around the "knee"
Samy Kaci, Gwenael Giacinti, Felix Aharonian, Jie-Shuang Wang
Published: 2025/10/1
Abstract
Recently, LHAASO detected a gamma-ray emission extending beyond $100\,\rm{TeV}$ from 4 sources associated to powerful microquasars. We propose that such sources are the main Galactic PeVatrons and investigate their contribution to the proton and gamma-ray fluxes by modeling their entire population. We find that the presence of only $\sim10$ active powerful microquasars in the Galaxy at any given time is sufficient to account for the proton flux around the knee and to provide a very good explanation of cosmic-ray and gamma-ray data in a self-consistent picture. The $10\,\rm{TeV}$ bump and the $300\,\rm{TeV}$ hardening in the cosmic-ray spectrum naturally appear, and the diffuse background measured by LHAASO above a few tens of $\rm{TeV}$ is accounted for. This supports the paradigm in which cosmic rays around the knee are predominantly accelerated in a very limited number of powerful microquasars.