Observation of photons above 300 TeV associated with a high-energy neutrino from the Cygnus region

Abstract

Galactic sites of acceleration of cosmic rays to energies of order 10^15 eV and higher, dubbed PeVatrons, reveal themselves by recently discovered gamma radiation of energies above 100 TeV. However, joint gamma-ray and neutrino production, which marks unambiguously cosmic-ray interactions with ambient matter and radiation, was not observed until now. In November 2020, the IceCube neutrino observatory reported an ~150 TeV neutrino event from the direction of one of the most promising Galactic PeVatrons, the Cygnus Cocoon. Here we report on the observation of a 3.1-sigma (post trial) excess of atmospheric air showers from the same direction, observed by the Carpet-2 experiment and consistent with a few-months flare in photons above 300 TeV, in temporal coincidence with the neutrino event. The fluence of the gamma-ray flare is of the same order as that expected from the neutrino observation, assuming the standard mechanism of neutrino production. This is the first evidence for the joint production of high-energy neutrinos and gamma rays in a Galactic source.

7 pages, 3 figures, AASTeX. V2: minor changes; Appendix with more analysis details added. Version accepted by Astrophys. J. Letters. V3: title corrected (text unchanged), matches the published version

References in corpus (10)

• First Detection of sub-PeV Diffuse Gamma Rays from the Galactic Disk: Evidence for Ubiquitous Galactic Cosmic Rays beyond PeV Energies
• HAWC observations of the acceleration of very-high-energy cosmic rays in the Cygnus Cocoon
• Identification of the TeV Gamma-ray Source ARGO J2031+4157 with the Cygnus Cocoon
• HAWC J2227+610 and its association with G106.3+2.7, a new potential Galactic PeVatron
• Evidence of 200 TeV photons from HAWC J1825-134
• On the IceCube spectral anomaly
• Neutrino telescopes and high-energy cosmic neutrinos
• Search for astrophysical PeV gamma rays from point sources with Carpet-2
• Carpet-2 search for PeV gamma rays associated with IceCube high-energy neutrino events
• Carpet-2 search for gamma rays above 100 TeV in coincidence with HAWC and IceCube alerts

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• Parameters of axion-like particles required to explain high-energy photons from GRB 221009A
• PeV photon and neutrino flares from galactic gamma-ray binaries
• Modeling of GeV-TeV gamma-ray emission of Cygnus Cocoon
• The LHAASO PeVatron bright sky: what we learned
• Ultra-High-Energy Gamma-Ray Astronomy
• Ultrahigh-energy diffuse gamma-ray emission from cosmic-ray interactions with medium surrounding acceleration sources
• Particle Acceleration in Mildly Relativistic Outflows of Fast Energetic Transient Sources
• PeV proton acceleration in Gamma-ray Binaries
• Probing the origin of cosmic rays in Cygnus Cocoon using ultrahigh-energy gamma-ray and neutrino observations
• Relativistic astrospheres of gamma-ray binaries: modeling of non-thermal processes
• Multimessenger Astronomy with Neutrinos
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• Upper limits on the isotropic diffuse flux of cosmic PeV photons from Carpet-2 observations
• How many VHE gamma-ray binaries with young pulsars can be observed?
• Constraining the position of the knee in the galactic cosmic ray spectrum with ultra-high-energy diffuse $\gamma$-rays