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Astrophysics > High Energy Astrophysical Phenomena

arXiv:2106.09865v2 (astro-ph)
[Submitted on 18 Jun 2021 (v1), revised 10 Sep 2021 (this version, v2), latest version 6 Jan 2026 (v3)]

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

Authors:The LHAASO collaboration
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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 $\gt$100 TeV with 9.5 sigma and 8.5 sigma, respectively. This source is not significantly favored as an extensive source with the angular extension smaller than the point-spread function of KM2A. The measured energy spectrum from 20 to 200 TeV can be approximately described by a power-law function with an index of -2.83$\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.
Comments: 12 pages, 7 figures, accepted by ApJL
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Cite as: arXiv:2106.09865 [astro-ph.HE]
  (or arXiv:2106.09865v2 [astro-ph.HE] for this version)
  https://doi.org/10.48550/arXiv.2106.09865
Related DOI: https://doi.org/10.3847/2041-8213/ac2579

Submission history

From: Sha Wu [view email]
[v1] Fri, 18 Jun 2021 01:44:30 UTC (1,395 KB)
[v2] Fri, 10 Sep 2021 14:44:38 UTC (501 KB)
[v3] Tue, 6 Jan 2026 10:14:10 UTC (371 KB)
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