Phys. Rev. Lett. 127, 031102 (2021) - Gamma-Ray Observation of the Cygnus Region in the 100-TeV Energy Region

Gamma-Ray Observation of the Cygnus Region in the 100-TeV Energy Region

M. Amenomori et al. (Tibet ${AS}_{γ}$ Collaboration)

Phys. Rev. Lett. 127, 031102 – Published 16 July 2021

Abstract

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 $J 2032 + 4127$ and the other mainly with a pulsar wind nebula PWN $G 75.2 + 0.1$ , 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.

Received 26 January 2021
Revised 30 April 2021
Accepted 15 June 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.031102

Physics Subject Headings (PhySH)

Cosmic ray acceleration Cosmic ray sources Gamma ray astronomy

Binary stars Neutron stars & pulsars

Cosmic ray & astroparticle detectors

Gravitation, Cosmology & Astrophysics

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Vol. 127, Iss. 3 — 16 July 2021

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Figure 1
Significance maps around the two gamma-ray emission sources detected above 10 TeV in the directions of Cygnus OB2 (a) and OB1 (b), smoothed by search windows (see the text). The point spread function (PSF) is shown in the inset figure. The red filled star with a position error circle is the centroid of TASG $J 2032 + 414$ -TASG $J 2019 + 368$ obtained by this work, while the magenta open cross is the centroid of VER $J 2031 + 415$ [20] in (a) and VER $J 2019 + 368$ [6] in (b) and the blue asterisk is that of HAWC $J 2031 + 415$ [12] in (a) and 3HWC $J 2019 + 367$ [23] in (b). The green filled diamonds show Fermi-LAT sources [42]. (a) The blue open triangle indicates the centroid of MAGIC $J 2031 + 4134$ [20]. The green filled diamond coincident with our gamma-ray emission centroid is the pulsar PSR $J 2032 + 4127$ . The sky-blue contours indicate 1420 MHz radio emissions provided by the Canadian Galactic Plane Survey [39], and the pink contours indicate $24 μ m$ infrared emissions by the Cygnus-X Spitzer Legacy Survey [40, 41]. (b) The white open circles are NuSTAR x-ray sources [33], and the gray filled inverted triangles are Wolf-Rayet stars [43]. The green filled diamond located at 0.23° east of our emission centroid is the pulsar PSR $J 2021 + 3651$ . The magenta open cross located at $(R . A ., Dec .) = (303.99 °, 37.21 °)$ is another VERITAS source VER $J 2016 + 371$ [6], which is not detected significantly in this work.
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Figure 2
Number of events observed with photon energies above 10 TeV as a function of the square of the opening angle between the estimated arrival direction and the centroid of TASG $J 2032 + 414$ in (a) and TASG $J 2019 + 368$ in (b). The red filled circles are the experimental data, with the best-fit Gaussian function indicated by the solid line. The blue histogram is the distribution of events expected by the MC simulation assuming a point-like gamma-ray source.
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Figure 3
Differential gamma-ray energy spectra of (a) TASG $J 2032 + 414$ and (b) TASG $J 2019 + 368$ with 95% C.L. upper limits measured by this work (red filled squares/arrows). In both panels, the blue filled circles/arrow (sky-blue open circles) show the gamma-ray spectrum of reported by VERITAS in 2018 (2014) [5, 6, 24], the gray open triangles/arrow by HAWC [11, 14], and the dark-green filled circles/arrows by ARGO [9]. Additionally in panel (a), the gold filled diamonds are reported by Fermi-LAT [6], the green open squares by MAGIC [4], and the pink pentagons/arrow by HEGRA [2]. The upper limits of Fermi-LAT, HAWC, and VERITAS are at the 95% confidence level, while those of HEGRA in (a) and ARGO in (b) are at the 99% and 90% confidence levels, respectively.
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Physical Review Letters

Gamma-Ray Observation of the Cygnus Region in the 100-TeV Energy Region

M. Amenomori et al. (Tibet ASγ Collaboration)

Phys. Rev. Lett. 127, 031102 – Published 16 July 2021

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M. Amenomori et al. (Tibet ${AS}_{γ}$ Collaboration)