Discovery of the Ultrahigh-energy Gamma-Ray Source LHAASO J2108+5157
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2021
- DOI:
- 10.3847/2041-8213/ac2579
- arXiv:
- arXiv:2106.09865
- Bibcode:
- 2021ApJ...919L..22C
- Keywords:
-
- Gamma-ray astronomy;
- Gamma-ray sources;
- Gamma-ray observatories;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 12 pages, 7 figures, accepted by ApJL