Galactic Super-Accreting X-ray Binaries as Super-PeVatron Accelerators

TL;DR

This paper proposes that galactic super-accreting X-ray binaries could be the sources of ultra-high-energy cosmic rays, acting as Super PeVatrons capable of accelerating protons beyond several PeV, and discusses their potential observational signatures.

Contribution

It introduces galactic super-accreting X-ray binaries as plausible sources of PeV cosmic rays and explores their acceleration mechanisms and observational signatures.

Findings

Super-accreting X-ray binaries can accelerate protons above several PeV.

Jets and winds from these binaries have kinetic energies exceeding 10^{39} erg/s.

Detection methods include ultra-high-energy gamma-ray halos and nebulae.

Abstract

The extension of the cosmic-ray (CR) spectrum well beyond 1~PeV necessitates the existence of a population of accelerators in the Milky Way, which we refer to as Super PeVatrons. Identifying the nature of these sources remains a challenge to the paradigm of galactic CRs. Galactic super-accreting X-ray binaries, where the compact object accretes at a rate near or above the Eddington limit, can meet the energy requirement to supply the high-energy population of galactic CRs. We demonstrate that the trans-relativistic jets and/or winds of these powerful objects with kinetic energy luminosity exceeding $10^{39} \, \rm erg/s$, can accelerate protons to energies above several PeV. Detection of such super-accreting X-ray binaries through their ultra-high-energy $\gamma$-ray ``halos" and large-scale nebulae is also discussed.