The link between extreme particle acceleration and X-ray binary jets
Year: 2026
Type: article
Abstract: The detection of multi-TeV radiation from several black-hole binaries has positioned the source class as a promising candidate to explain the observed cosmic-ray flux in the PeV energy range. We aim to determine what distinguishes the systems detected in the gamma-ray range from the rest of the population. We built on existing catalogues of black-hole binaries by including information on the radio and gamma-ray emission from these systems. We then compared the $>100$ TeV gamma-ray luminosity to different properties of the systems and evaluated the strength of the (rank) correlation (τ_K) between them. Additionally, we compared the distribution of sources in our sample with the positions of unassociated gamma-ray sources in the 1LHAASO and 1HGPS catalogues to determine whether a correlation exists between them. We find no correlation with the mass of the compact object, the companion mass, or the inclination angle. Instead, we find evidence for a strong correlation (τ_K>0.5) between the gamma-ray luminosity and the radio and hard-state luminosities in our sample. The limited number of gamma-ray detections means that this correlation cannot yet be claimed as statistically significant. We find indications that a high (≳ 20%) duty cycle (defined as the fraction of time spent in outburst) might be a requirement for $>100$ TeV gamma-ray loudness. We find significant evidence ($>3σ$) that black-hole binaries are located near unassociated gamma-ray sources in the region of the sky not covered by LHAASO. This evidence is only significant when comparing to binaries detected in the radio band, not for the sample without a reported radio detection. We conclude that radio-bright black-hole binaries with a high duty cycle are more likely to be detected as gamma-ray sources than sources that are not detected in the radio band or those with low duty cycles. This result suggests that the particles responsible for the gamma-ray emission are associated with the jets, either accelerated within them or via their interaction with their surroundings.
Source: Astronomy and Astrophysics
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7223143489