Volume 395 - 37th International Cosmic Ray Conference (ICRC2021) - GAI - Gamma Ray Indirect
Gamma-ray Observation of the Cygnus Region with the Tibet Air Shower Array
Y. Katayose*  on behalf of the Tibet ASgamma Collaboration
Full text: pdf
Pre-published on: July 20, 2021
Published on: March 18, 2022
Abstract
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 is 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, by means of 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 5.3$\sigma$(4.7$\sigma$) in the direction centered on (R.A., Dec) = (308.04$^\circ\pm$
0.08$^\circ$, 41.4$^\circ\pm$0.06$^\circ$), which was associated with 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 $\pm$ 0.83) $\times$ 10$^{-16}$ (E/40 TeV)$^{3.12\pm 0.12}$ TeV$^{-1}$cm$^{-2}$s$^{-1}$.
The other had an excess of pre-trial(post-trial) detection significance of 6.7$\sigma$(6.2$\sigma$) in the direction centered on
(R.A., Dec)=(304.99$^{\circ}\pm$ 0.11$^{\circ}$, 36.84$^{\circ}\pm$0.08$^{\circ})$,
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 $\pm$ 1.3) $\times$ 10$^{-16}$ (E/40 TeV)$^{2.70\pm 0.13}$ TeV$^{-1}$cm$^{-2}$s$^{-1}$, or including an exponential cutoff as
dF/dE = (3.6 $\pm$ 2.0) $\times$ 10$^{-15}$ (E/40 TeV)$^{1.60\pm 0.5}$ exp(E/(44$\pm$ 21TeV))} TeV$^{-1}$cm$^{-2}$s$^{-1}$
DOI: https://doi.org/10.22323/1.395.0799
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