33 research outputs found
First Detection of Photons with Energy Beyond 100 TeV from an Astrophysical Source
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 muon number measured in an air shower, we
successfully suppress 99.92% of the cosmic-ray background events with energies
TeV. As a result, we observed 24 photon-like events with TeV
against 5.5 background events, which corresponds to 5.6 statistical
significance. This is the first detection of photons with TeV from an
astrophysical source.Comment: April 4, 2019; Submitted to the Physical Review Letter
Observation of gamma rays up to 320 TeV from the middle-aged TeV pulsar wind nebula HESS J1849000
Gamma rays from HESS J1849000, 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, in units of Gaussian standard
deviation . The energy spectrum measured between for the first time is described with a simple power-law
function of . 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 J18490001.
On the other hand, the gamma-ray energy spectrum can also be 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 , cut is estimated at , suggesting that
protons are accelerated up to the PeV energy range. Our study thus proposes
that HESS J1849000 should be further investigated as a new candidate for a
Galactic PeV cosmic-ray accelerator, PeVatron.Comment: 10 pages, 2 figures, Accepted for publication from the Astrophysical
Journa