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.

12 pages, 7 figures, accepted by ApJL

References in corpus (3)

• Detection of the Characteristic Pion-Decay Signature in Supernova Remnants
• Physical properties of molecular clouds for the entire Milky Way disk
• The observation of the Crab Nebula with LHAASO-KM2A for the performance study

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• Supernova connection of unidentified ultra high energy gamma-ray source LHAASO J2108+5157
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