First constraints on the strength of the extragalactic magnetic field from γ-ray observations of GRB 221009A
Abstract
The extragalactic magnetic field (EGMF) could be probed with γ-ray observations of distant sources. Primary very high-energy γ-rays from these sources absorb on extragalactic background light photons, and secondary electrons/positrons from the pair production acts create cascade γ-rays. These cascade γ-rays could be detected with space γ-ray telescopes such as Fermi-LAT. The γ-ray burst GRB 221009A was an exceptionally bright transient well suited for intergalactic γ-ray propagation studies. Using publicly available Fermi-LAT data, we obtain upper limits on the spectrum of delayed emission from GRB 221009A during the time windows of 10, 30, and 90 d after the burst, and compare these with model spectra calculated for various EGMF strengths B, obtaining constraints on B. We show that the values of B between 10-20 and 10-18 G are excluded.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2024
- DOI:
- 10.1093/mnrasl/slad142
- arXiv:
- arXiv:2306.05347
- Bibcode:
- 2024MNRAS.527L..95D
- Keywords:
-
- magnetic fields;
- methods: data analysis;
- methods: numerical;
- gamma-ray burst: individual: GRB 221009A;
- gamma-rays: general;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 8 pages, 11 figures. Moderate changes w.r.t. v1. Accepted for publication in MNRAS Lett. This is the authors's version and not the final typeset