Galactic Superaccreting X-Ray Binaries as Super-PeVatron Accelerators

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 superaccreting X-ray binaries (XRBs), 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 transrelativistic jets and/or winds of these powerful objects with kinetic power exceeding 10 39 erg s −1 can accelerate protons to energies above several PeV. Detection of such superaccreting XRBs through their ultrahigh-energy gamma-ray “halos” and large-scale nebulae is also discussed.