Constraints on Axion-like Particles from the Observation of GRB 221009A by LHAASO

TL;DR

This study uses gamma-ray data from the brightest GRB 221009A to set new constraints on axion-like particles by analyzing photon oscillations in different magnetic field models of the host galaxy and the Milky Way.

Contribution

It introduces a novel analysis of ALP-photon oscillations using recent GRB gamma-ray spectra and compares constraints across multiple magnetic field models of the host galaxy.

Findings

Constraints on ALP parameters are comparable across different host galaxy magnetic field models.

Results provide complementary bounds in the small ALP mass region.

The study enhances understanding of ALP effects in high-energy astrophysical phenomena.

Abstract

The LHAASO collaboration recently reported the measurement of the gamma-ray spectra of GRB 221009A, which is the brightest burst ever, covering an energy range from 0.3 $\mathrm{TeV}$ to about 10 $\mathrm{TeV}$. Based on the observation, we investigate the ALP-photon oscillation effect in the host galaxy of GRB 221009A and the Milky Way. The ${\rm CL_s}$ method is applied to set constraints on the ALP parameters in this study. Given the uncertain magnetic field configuration in the host galaxy, we use three different models: a homogeneous magnetic field model, a magnetic field model identical to that of the Milky Way, and a model constructed from the HST observations of the host galaxy. We find that the constraints derived using these three host galaxy magnetic field models are comparable. Our results are complementary in the small ALP mass regions compared with other experiments.