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雨森 道紘*; 土屋 晴文; Tibet AS
Collaboration*; 他116名*
Astrophysical Journal, 954(2), p.200_1 - 200_7, 2023/09
被引用回数：1 パーセンタイル：44.78(Astronomy & Astrophysics)Gamma rays from HESS J1849-000, a middle-aged TeV pulsar wind nebula (PWN), are observed by the Tibet air shower array and the muon detector array. The detection significance of gamma rays reaches 
and 
levels above 25 TeV and 100 TeV, respectively. The energy spectrum measured between 40 TeV 
E 320 TeV for the first time is described with a simple power-law function of dN/dE = 
. The gamma-ray energy spectrum from the sub-TeV to sub-PeV ranges including the results of previous studies can be modeled with the leptonic scenario, Inverse Compton Scattering by high-energy electrons accelerated by the PWN of PSR J1849-0001, but the scenario requires sophisticated theoretical modeling. On the other hand, the gamma-ray energy spectrum can be simply modeled with the hadronic scenario in which gamma rays are generated from the decay of neutral pions produced by collisions between accelerated cosmic-ray protons and the ambient molecular cloud found in the gamma-ray emitting region. The cutoff energy of cosmic-ray protons 
is estimated at 
, suggesting that protons are accelerated up to the PeV energy range. Our study proposes that HESS J1849-000 should be further investigated as a new candidate for a Galactic PeV cosmic-ray accelerator, or "PeVatron".
雨森 道紘*; 土屋 晴文; Tibet AS
Collaboration*; 他111名*
Physical Review Letters, 127(3), p.031102_1 - 031102_6, 2021/07
被引用回数：18 パーセンタイル：86.79(Physics, Multidisciplinary)We report observations of gamma-ray emissions with energies in the 100-TeV energy region from the Cygnus region in our Galaxy. Two sources are significantly detected in the directions of the Cygnus OB1 and OB2 associations. Based on their positional coincidences, we associate one with a pulsar PSR J2032 + 4127 and the other mainly with a pulsar wind nebula PWN G75.2 + 0.1, with the pulsar moving away from its original birthplace situated around the centroid of the observed gamma-ray emission. This work would stimulate further studies of particle acceleration mechanisms at these gamma-ray sources.
雨森 道紘*; 土屋 晴文; Tibet AS Collaboration*; 他93名*
Nature Astronomy (Internet), 5(5), p.460 - 464, 2021/05
被引用回数：66 パーセンタイル：98.88(Astronomy & Astrophysics)Cosmic rays (protons and other atomic nuclei) are believed to gain energies of petaelectronvolts (PeV) and beyond at astrophysical particle accelerators called "PeVatrons" inside our Galaxy. Although a characteristic feature of a PeVatron is expected to be a hard gamma-ray energy spectrum that extends beyond 100 teraelectronvolts (TeV) without a cut-off, none of the currently known sources exhibit such a spectrum owing to the low maximum energy of accelerated cosmic rays or owing to insufficient detector sensitivity around 100 TeV. Here, we report the observation of gamma-ray emission from the supernova remnant G106.3+2.7 above 10 TeV. This work provides flux data points up to and above 100 TeV and indicates that the very-high-energy gamma-ray emission above 10 TeV is well correlated with a molecular cloud rather than with the pulsar PSR J2229+6114. Regarding the gamma-ray emission mechanism of G106.3+2.7, this morphological feature appears to favour a hadronic origin via the 
decay caused by accelerated relativistic protons over a leptonic origin via the inverse Compton scattering by relativistic electrons. Furthermore, we point out that an X-ray flux upper limit on the synchrotron spectrum would provide important information to firmly establish the hadronic scenario as the mechanism of particle acceleration at the source.
雨森 道紘*; 土屋 晴文; Tibet AS Collaboration*; 他93名*
Physical Review Letters, 126(14), p.141101_1 - 141101_7, 2021/04
被引用回数：119 パーセンタイル：99.56(Physics, Multidisciplinary)We report, for the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk. Particularly, all gamma rays above 398 TeV are observed apart from known TeV gamma-ray sources and compatible with expectations from the hadronic emission scenario in which gamma rays originate from the decay of 
's produced through the interaction of protons with the interstellar medium in the Galaxy. This is strong evidence that cosmic rays are accelerated beyond PeV energies in our Galaxy and spread over the Galactic disk.
雨森 道紘*; 土屋 晴文; Tibet AS Collaboration*; 他89名*
Physical Review Letters, 123(5), p.051101_1 - 051101_6, 2019/08
被引用回数：125 パーセンタイル：98.49(Physics, Multidisciplinary)We report on the highest energy photons from the Crab Nebula observed by the Tibet air shower array with the underground water-Cherenkov-type muon detector array. Based on the criterion of a muon number measured in an air shower, we successfully suppress 99.92% of the cosmic-ray background events with energies 
100 TeV. As a result, we observed 24 photon like events with 100 TeV against 5.5 background events, which corresponds to a 5.6
statistical significance. This is the first detection of photons with 100 TeV from an astrophysical source.
