Light speed variation from GRB 221009A

Abstract

It is postulated in Einstein's relativity that the speed of light in vacuum is a constant for all observers. However, the effect of quantum gravity could bring an energy dependence of light speed, and a series of previous researches on high-energy photon events from gamma-ray bursts (GRBs) and active galactic nuclei (AGNs) suggest a light speed variation \(v(E)=c\left(1-E / E_{\mathrm{LV}}\right)\) with \(E_{\mathrm{LV}}=3.6 \times 10^{17} ~\mathrm{GeV}\). From the newly detected gamma-ray burst GRB 221009A, we find that a \(99.3~\)GeV photon detected by Fermi-LAT is coincident with the sharp spike in the light curves detected by Fermi-GBM and HEBS under the above scenario of light speed variation, suggesting that this high energy photon was emitted at the same time with a sharp spike of low energy photon emission at the GRB source. Thus this highest energy photon event detected by Fermi-LAT during the prompt emission of gamma ray bursts supports the linear form modification of light speed in cosmological space.