2026/05/04 by Tsunefumi Mizuno, Hidetoshi Sano, Takeru Murase +3
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Astrophysical Phenomena and Observations #Gamma-ray bursts and supernovae
paper · pdf · doi:10.3847/1538-4357/ae680d
Abstract Large High Altitude Air Shower Observatory (LHAASO) has reported 43 sub-PeV γ -ray sources, which are promising candidates for cosmic-ray (CR) accelerators above the PeV energy, commonly called PeVatrons. Multiwavelength observations are crucial for identifying the underlying particle species and estimating the CR energy content of these sources. In this work we investigate the region around LHAASO J1912+1014u (and HESS J1912+101) using Fermi-LAT γ -ray data and FUGIN CO data. We analyzed 15 yr of Fermi-LAT data in the 0.4–409.6 GeV energy range. By improving the standard Fermi-LAT diffuse emission model, we significantly reduced the large residuals around the source in the 1.6–12.8 GeV band. We detected a statistically significant excess above the diffuse background, which likely represents ≥10 GeV emission associated with the LHAASO/H.E.S.S. source. The GeV excess exhibits a hard spectrum (photon index of about 2.1) and is well reproduced by interstellar gas templates with systemic velocities of about 25 km s −1 or 60 km s −1 . We performed a comprehensive fit to the GeV–TeV spectral energy distribution. Although a leptonic scenario can reproduce the observed spectrum, a hadronic scenario is favored once electron cooling is considered. The inferred CR proton spectrum has an index of ∼2.2, and the total CR proton energy above 1 GeV is (1–5) × 10 49 erg, depending on the assumed velocity range of the associated interstellar gas. A stringent upper limit on diffuse X-ray emission further supports the proton PeVatron scenario.