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

Abstract

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 $100\mathrm{TeV}$ 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 $0.34^{\circ }\pm 0.12^{\circ }$ is successfully detected above $25\mathrm{TeV}$ at $(\hat{I}\pm ,\hat{I}´)=(281.09^{\circ }\pm 0.10^{\circ },-3.76^{\circ }\pm 0.09^{\circ })$ near HESS J1843$-$033 with a statistical significance of $6.2\ddot{I}ƒ$, 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 $25\mathrm{TeV}<E<130\mathrm{TeV}$ is described with $\mathrm{d}N/\mathrm{d}E=(9.70\pm 1.89)\times 10^{-16}(E/40\mathrm{TeV}{)}^{-3.26\pm 0.30}{\mathrm{TeV}}^{-1}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$, 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 $49.5\pm 9.0\mathrm{TeV}$. Associations of TASG J1844-038 with SNR G28.6$-$0.1 and PSR J1844-0346 are also discussed in detail for the first time.

11 pages, 4 figures, 1 table