New Tests on Lorentz Invariance Violation Using Energy-Resolved Polarimetry of Gamma-Ray Bursts

Abstract

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 $\eta$ characterizing the broken degree of Lorentz invariance can be constrained to be $|\eta |<\mathcal{O}(10^{-15}-10^{-16})$, which represent an improvement of at least eight orders of magnitude over existing limits from multi-band 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 $\eta$ are statistically more robust. Future polarization measurements of GRBs at higher energies and larger distances would further improve LIV limits through the birefringent effect.

Comments: 8 pages, 2 figures, 1 table. Accepted for publication in ApJ