Observation of multi-ten TeV to sub-PeV gamma rays from the HESS J1843-033 region with the Tibet air shower array

Abstract

The sky region around HESS J1843-033, a southern TeV gamma-ray source, is observed by the Tibet air shower array equipped with an underground muon detector array. The analysis makes use of the data taken from February 2014 to May 2017. A gamma-ray source TASG J1844-038 is detected above $25\, {\rm TeV}$ with a $6.2\, \sigma$ level, and its position is statistically consistent with that of nearby gamma-ray sources including HESS J1843-033. The energy spectrum is measured for the first time between $25$ and $130\, {\rm TeV}$ and is described with ${\rm d}N/{\rm d}E = (9.70\pm 1.89)\times 10^{-16}(E/40\, {\rm TeV})^{-3.26\pm 0.30}\, {\rm TeV}^{-1}\, {\rm cm}^{-2}\, {\rm s}^{-1}$. The spectrum smoothly connects to that of HESS J1843-033 in the lower energy range and is consistent with the flux of LHAASO J1843-0338 at $100\, {\rm TeV}$, and the fit to the combined spectra of the TASG, H.E.S.S., and LHAASO sources implies the cutoff at $49.5\pm 9.0\, {\rm TeV}$ in the gamma-ray spectrum. The association of TASG J1844-038 with a nearby supernova remnant G28.6-0.1 and a gamma-ray pulsar J1844-0346 is discussed.