Abstract
We report the discovery of an ultrahigh-energy (UHE) gamma-ray source, LHAASO J2108+5157, by analyzing the LHAASO-KM2A data of 308.33 live days. A significant excess of gamma ray-induced showers is observed in both energy bands of 25-100 and >100 TeV with 9.5σ and 8.5σ, respectively. This source is not significantly favored as an extended source with an 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 ± 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, and deeper multiwavelength observations will help to cast new light on this intriguing UHE source.
Recommended Citation
"Discovery Of The Ultrahigh-energy Gamma-Ray Source LHAASO J2108+5157," Astrophysical Journal Letters, vol. 919, no. 2, article no. L22, American Astronomical Society; IOP Publishing, Oct 2021.
The definitive version is available at https://doi.org/10.3847/2041-8213/ac2579
Department(s)
Physics
Publication Status
Free Access
Keywords and Phrases
Gamma-ray astronomy; Gamma-ray observatories; Gamma-ray sources
International Standard Serial Number (ISSN)
2041-8213; 2041-8205
Document Type
Article - Journal
Document Version
Final Version
File Type
text
Language(s)
English
Rights
© 2025 The Authors, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution 4.0 License.
Publication Date
01 Oct 2021
