A delayed 400 GeV photon from GRB 221009A and implication on the intergalactic magnetic field.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38769312.
- Also identified by DOI 10.1038/s41467-024-48668-5 and PMC identifier 11106316.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Large High Altitude Air Shower Observatory has detected 0.2 - 13 TeV emission of GRB 221009A within 2000 s since the trigger. Here we report the detection of a 400 GeV photon, without accompanying prominent low-energy emission, by Fermi Large Area Telescope in this direction with a 0.4 days' delay. Given an intergalactic magnetic field strength of about 4 × 10<sup>-17</sup> G, which is comparable to limits from TeV blazars, the delayed 400 GeV photon can be explained as the cascade emission of about 10 TeV gamma rays. We estimate the probabilities of the cascade emission that can result in one detectable photon beyond 100 GeV by Fermi Large Area Telescope within 0.3 - 1 days is about 2% whereas it is about 20.5% within 0.3 - 250 days. Our results show that Synchrotron Self-Compton explanation is less favored with probabilities lower by a factor of about 3 - 30 than the cascade scenario.