Astroparticles from X-ray Binary Coronae

TL;DR

This paper proposes that the coronae of accreting stellar-mass black holes in X-ray binaries are significant sources of high-energy neutrinos and gamma rays, potentially explaining observed astrophysical phenomena and contributing to Galactic cosmic rays.

Contribution

It introduces a model linking XRB coronae to high-energy neutrino and gamma-ray emission, connecting microquasar physics to Galactic cosmic-ray sources.

Findings

Coronal regions in XRBs can produce neutrinos and gamma rays through particle acceleration.

The model explains GeV gamma-ray emission during the hard state of Cygnus X-1.

XRB coronae could significantly contribute to the Galactic neutrino flux.

Abstract

The recent observation of high-energy neutrinos from the Galactic plane implies an abundant population of hadronic cosmic-ray sources in the Milky Way. We explore the role of the coronae of accreting stellar-mass black holes as such astroparticle emitters. We show that the particle acceleration and interaction timescales in the coronal region are tied to the compactness of the X-ray source. Thus, neutrino emission processes may similarly happen in the cores of active galactic nuclei and black hole X-ray binaries (XRB), despite of their drastically different masses and physical sizes. We apply the model to the well-measured XRB Cygnus X-1 and find that the cascaded gamma rays accompanying the neutrino emission naturally explain the GeV emission that only presents during the source's hard state, while the state-averaged gamma-ray emission explains the LHAASO observation above 20 TeV. We show that XRB coronae could contribute significantly to the Galactic cosmic-ray and Galactic plane neutrino fluxes. Our model predicts variable high-energy neutrino emission from bright Galactic XRBs that may be observed by IceCube and future neutrino observatories.