2025ApJ...983..164W

One of the manifestations of Lorentz invariance violation (LIV) is vacuum birefringence, which leads to an energy-dependent rotation of the polarization plane of linearly polarized photons arising from an astrophysical source. Here we use the energy-resolved polarization measurements in the prompt gamma-ray emission of five bright gamma-ray bursts (GRBs) to constrain this vacuum birefringent effect. Our results show that at the 95% confidence level, the birefringent parameter η characterizing the broken degree of Lorentz invariance can be constrained to be $| \eta | \lt { \mathcal O }(1{0}^{-15}-1{0}^{-16})$, which represents an improvement of at least 8 orders of magnitude over existing limits from multiband optical polarization observations. Moreover, our constraints are competitive with previous best bounds from the single gamma-ray polarimetry of other GRBs. We emphasize that, thanks to the adoption of the energy-resolved polarimetric data set, our results on η are statistically more robust. Future polarization measurements of GRBs at higher energies and larger distances would further improve LIV limits through the birefringent effect.