Using LHASSO-observed Gamma-Ray Bursts to Study the Extragalactic Background Light

Abstract The extragalactic background light (EBL), a diffuse radiation field produced by all galaxies throughout cosmic history, plays a crucial role in the propagation of high-energy gamma-rays through photon–photon interactions. These interactions lead to characteristic absorption features in the observed TeV gamma-ray spectrum. Motivated by these effects, we analyze observations of GRB 221009A, the most energetic gamma-ray burst (GRB) ever detected by the Large High Altitude Air Shower Observatory, to investigate the EBL via gamma–gamma absorption signatures imprinted on the TeV spectrum. To minimize potential effects from Lorentz invariance violation and axion-like particles, we restrict our analysis to gamma rays with energies below 8 TeV. By comparing the modeled intrinsic spectra with the observed data, we constrain the spectral energy distribution of the EBL in the wavelength range of 0.1–40 μ m. Our results are consistent with existing EBL models and observational limits derived from galaxy counts and infrared surveys. Furthermore, the inferred cosmic emissivity, which represents the integrated light from galaxies, is found to be primarily dominated by spiral-type galaxies.