Possible Evidence for Lorentz Invariance Violation in Gamma-ray Burst 221009A

TL;DR

This paper examines gamma-ray burst 221009A's high-energy photon detections and suggests that Lorentz invariance violation at certain energy scales could explain the survival of extremely energetic photons, indicating possible new physics.

Contribution

It provides the first potential evidence for subluminal Lorentz invariance violation based on gamma-ray observations and constrains the violation energy scale using recent high-energy detections.

Findings

Detection of 18 TeV photon is consistent with background models.

Detection of 251 TeV photon is highly unlikely without new physics.

Lorentz invariance violation could occur below the Planck scale.

Abstract

The preliminary detections of the gamma-ray burst 221009A up to 18 TeV by LHAASO and up to 251 TeV by Carpet 2 have been reported through Astronomer's Telegrams and Gamma-ray Coordination Network circulars. Since this burst is at redshift $z=0.1505$, these photons may at first seem to have a low probability to avoid pair production off of background radiation fields and survive to reach detectors on Earth. By extrapolating the reported $0.1-1.0$\ GeV LAT spectrum from this burst to higher energies and using this to limit the intrinsic spectrum of the burst, we show that the survival of the 18 TeV photon detected by LHAASO is not unlikely with many recent extragalactic background light models, although the detection of a 251 TeV event is still very unlikely. This can be resolved if Lorentz invariance is violated at an energy scale $E_{\rm QG}< 49 E_{\rm Planck}$\ in the linear ($n=1$) case, and $E_{\rm QG}< 10^{-6}E_{\rm Planck}$\ in the quadratic ($n=2$) case (95\% confidence limits), where $E_{\rm Planck}$ is the Planck energy. This could potentially be the first evidence for subluminal Lorentz invariance violation.