Measurement of the Gamma-Ray Energy Spectrum beyond 100 TeV from the HESS J1843-033 Region

HESS J1843-033 is a very high energy gamma-ray source whose origin remains unidentified. This work presents, for the first time, the energy spectrum of gamma rays beyond 100 TeV from the HESS J1843-033 region using the data recorded by the Tibet air shower array and its underground muon detector array. A gamma-ray source with an extension of 0.°34 ± 0.°12 is successfully detected above 25 TeV at (α, δ) = (281.°09 ± 0.°10, -3.°76 ± 0.°09) near HESS J1843-033 with a statistical significance of 6.2σ, and the source is named TASG J1844-038. The position of TASG J1844-038 is consistent with those of HESS J1843-033, eHWC J1842-035, and LHAASO J1843-0338. The measured gamma-ray energy spectrum in 25 TeV < E < 130 TeV is described with ${dN}/{dE}=(9.70\pm 1.89)\times {10}^{-16}$ (E/40 TeV)^-3.26±0.30 TeV^-1 cm^-2 s^-1, and the spectral fit to the combined spectra of HESS J1843-033, LHAASO J1843-0338, and TASG J1844-038 implies the existence of a cutoff at 49.5 ± 9.0 TeV. Associations of TASG J1844-038 with SNR G28.6-0.1 and PSR J1844-0346 are also discussed in detail for the first time.