Microquasars as the major contributors to Galactic cosmic rays around the "knee"

TL;DR

This paper suggests that a small number of powerful microquasars in our galaxy are the main sources of cosmic rays around the knee, explaining observed gamma-ray and cosmic-ray features.

Contribution

It models the entire population of microquasars and demonstrates their sufficiency in explaining cosmic-ray and gamma-ray data around the knee.

Findings

Approximately 10 active microquasars can account for the proton flux around the knee.

The model naturally explains the 10 TeV bump and 300 TeV hardening in cosmic-ray spectrum.

The diffuse gamma-ray background above tens of TeV is consistent with microquasar contributions.

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.