Gamma-ray Observation of the Cygnus Region with the Tibet Air Shower

The Tibet-III air shower array and underground water-Cherenkov-type muon detector array have been successfully operated since 2014, at an altitude of 4,300m in Tibet, China. The gamma-ray energy and arrival direction are determined by the Tibet AS array, while the MD array enables us to suppress more than 99.9% of background cosmic rays above 100 TeV, using counting number of muons in an air shower at 2.4 m underground. We surveyed gamma-ray emissions in the energy region above 10 TeV from the Cygnus region in our Galaxy. Two sources were significantly detected in the directions of the Cygnus OB1 and OB2 associations. One of the gamma-ray emissions had an excess of pre-trial(post-trial) detection significance of 5.3σ(4.7σ) in the direction centered on (R.A., Dec) = (308.04◦ ± 0.08◦,41.46◦±0.06◦), whichwas associatedwith Pulsar PSR J2032+4127. The obtained spectrum from 10 TeV to120 TeV can be expressed by a simple power-law as dF/dE = (4.13 ± 0.83) × 10−16(E/40TeV)3.12±0.12 TeV−1cm−2s−1. The other had an excess of pre-trial(post-trial) detection significance of 6.7σ(6.2σ) in the direction centered on (R.A., Dec) = (304.99◦ ± 0.11◦,36.84◦ ± 0.08◦), which was associated 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. The obtained spectrum from 10 TeV to 200 TeV can be expressed by a simple power-law as dF/dE = (10.6 ± 1.3) × 10−16(E/40TeV)2.70±0.13 TeV−1cm−2s−1, or including an exponential cutoff as dF/dE = (3.6 ± 2.0) × 10−15(E/40TeV)1.60±0.5 exp (E/(44 ± 21TeV)) TeV−1cm−2s−1.