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 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 ± 1.89 ) × 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.

HAWC Study of the Very-high-energy γ-Ray Spectrum of HAWC J1844−034

“…In the figure, the TeV γ-ray flux data points from Tibet AS-Gamma (green) and LHAASO (purple) at 100 TeV have also been added for comparison (Cao et al 2021;Amenomori et al 2022). The fitted HAWC spectrum is in good agreement with the results from both LHAASO and Tibet AS-Gamma.…”

“…, at 20 TeV (Amenomori et al 2022). This may be due to the different conditions we are performing the fits in, such as the energy range, pivot energy, and spectral model.…”

“…Furthermore, from Amenomori et al (2022), the diffusion timescale for protons can be estimated using where χ is the factor of diffusion suppression, and R sys is the radius of the emission region. For the calculation, a χ of 0.1 and B of 10 μG are assumed (Amenomori et al 2022). Using R sys = (0°.48 πd src )/180°∼ 80 pc and E p = 169 TeV (cutoff energy from the best-fit proton spectrum), we can obtain a τ diff of ∼5 kyr, which is indeed smaller than the known age of SNR G28.6−0.1 of 19 kyr (Ranasinghe & Leahy 2018).…”

“…Figure8. Spectral distribution plot of the best-fit leptonic (blue) and hadronic (red) scenarios that have been fitted using the TeV γ-ray flux points speculated to have the same original source (H.E.S.S.Collaboration et al 2018;Cao et al 2021;Amenomori et al 2022). The error bands indicate statistical errors.…”

Summary of Session III: Multimessenger astrophysics

“…The energy spectrum of photons can be explained by Inverse Compton scattering of electrons. A series of further gamma-ray observations at 100 TeV, were published recently, with a potential Supernovae Remnant (SNR) PeVatron G106.3+2.7 [20], and sources in Cygnus [21] and HESS J1843-033 [22] regions. An observation of sub-PeV diffuse gamma rays from the Milky Way galaxy were reported in 2021 [23], with no correlation with the known TeV sources.…”