Discovery of the Ultra-high energy gamma-ray source LHAASO J2108+5157

Abstract

We report the discovery of a UHE gamma-ray source, LHAASO J2108+5157, by analyzing the LHAASO-KM2A data of 308.33 live days. Significant excess of gamma-ray induced showers is observed in both energy bands of 25-100 TeV and $>$100 TeV with 9.5 sigma and 8.5 sigma, respectively. This source is not significantly favored as an extensive source with the angular extension smaller than the point-spread function of KM2A. The measured energy spectrum from 20 to 200 TeV can be approximately described by a power-law function with an index of -2.83$\pm$ 0.18stat. A harder spectrum is demanded at lower energies considering the flux upper limit set by Fermi-LAT observations. The position of the gamma-ray emission is correlated with a giant molecular cloud, which favors a hadronic origin. No obvious counterparts have been found, deeper multiwavelength observations will help to shed new light on this intriguing UHE source.

arXiv comment12 pages, 7 figures, accepted by ApJL

References in corpus (18)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• The Milky Way in Molecular Clouds: A New Complete CO Survey
• Fermi Large Area Telescope Fourth Source Catalog
• Detection of the Characteristic Pion-Decay Signature in Supernova Remnants
• Acceleration of petaelectronvolt protons in the Galactic Centre
• Development of the Model of Galactic Interstellar Emission for Standard Point-Source Analysis of Fermi Large Area Telescope Data
• Physical properties of molecular clouds for the entire Milky Way disk
• Discovery of very high energy gamma-ray emission coincident with molecular clouds in the W28 (G6.4-0.1) field
• Multiple Galactic Sources with Emission Above 56 TeV Detected by HAWC
• First Detection of Photons with Energy Beyond 100 TeV from an Astrophysical Source
• Pass 8: Toward the Full Realization of the Fermi-LAT Scientific Potential
• Swift X-ray Telescope Monitoring of Fermi-LAT Gamma Ray Sources of Interest
• The observation of the Crab Nebula with LHAASO-KM2A for the performance study
• New galactic open cluster candidates from DSS and 2MASS imagery
• On the evolution of the Gamma- and X-ray luminosities of Pulsar Wind Nebulae
• Fermi-LAT improved Pass~8 event selection
• Tests of Statistical Significance and Background Estimation in Gamma Ray Air Shower Experiments
• Leaked GeV CRs from a broken shell: Explaining 9 years Fermi-LAT data of SNR W28

Cited by in corpus (21)

• The First LHAASO Catalog of Gamma-Ray Sources
• Measurement of ultra-high-energy diffuse gamma-ray emission of the Galactic plane from 10 TeV to 1 PeV with LHAASO-KM2A
• The energy spectrum of cosmic rays beyond the turn-down around $10^{17}$ eV as measured with the surface detector of the Pierre Auger Observatory
• Beginning a journey across the universe: the discovery of extragalactic neutrino factories
• On the potential of bright, young pulsars to power ultra-high gamma-ray sources
• A search for photons with energies above $2\times 10^{17}$ eV using hybrid data from the low-energy extensions of the Pierre Auger Observatory
• PeV photon and neutrino flares from galactic gamma-ray binaries
• Multi-wavelength study of the galactic PeVatron candidate LHAASO J2108+5157
• The LHAASO PeVatron bright sky: what we learned
• Neutrino Observations of LHAASO Sources: Present Constraints and Future Prospects
• Modeling of GeV-TeV gamma-ray emission of Cygnus Cocoon
• Ultra-high Energy Gamma-rays from Past Explosions in our Galaxy
• Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario
• Supernova connection of unidentified ultra high energy gamma-ray source LHAASO J2108+5157
• Evidence for a gamma-ray molecular target in the enigmatic PeVatron candidate LHAASO J2108+5157
• Escape of cosmic rays from perpendicular shocks in the circumstellar magnetic field
• Searching for TeV emission from LHAASO J0341+5258 with VERITAS and HAWC
• VERITAS and HAWC observations of unidentified source LHAASO J2108+5157
• Study of Ultra-High-Energy Gamma-Ray Source 1LHAASO J0056+6346u and Its Possible Origins
• Are Kronberger 80 and/or Kronberger 82 regions PeVatron candidates for LHAASO J2108+5157?
• Can superbubbles accelerate ultra-high energy protons?