Spectral evolution responsible for the transition from positive lags to negative lags in Gamma-ray Bursts

TL;DR

This paper investigates the cause of spectral lag transitions in gamma-ray bursts, concluding that spectral evolution, not Lorentz Invariance Violation, explains the observed shift from positive to negative lags.

Contribution

The study demonstrates that spectral evolution, rather than LIV, accounts for the lag transition in GRBs, providing new insights into GRB emission mechanisms.

Findings

Spectral evolution explains the lag transition in GRB 190530A.

LIV models are incompatible with current spectral lag observations.

Spectral lag transitions are due to intrinsic spectral evolution, not new physics.

Abstract

It was well known that most of gamma-ray bursts (GRBs) are dominated by positive spectral lags, while a small fraction of GRBs show negative lags. However, Wei et al. firstly identified a well-defined transition from positive lags to negative lags in GRB 160625B, and then got robust limits on possible violation of Lorentz Invariance (LIV) based on the observation. Recently, such a transition has been found in three different emission episodes in \thisgrb by Gunapati et al., which provides us a great opportunity to investigate whether the transition results from LIV-induced observed spectral lags. Our analysis shows that the LIV model can not be compatible with the current observations, whereas, only the spectral evolution induced spectral lags could responsible for the transition. So, spectral evolution can also explain the positive to negative lag in GRB 190530A.