![]() Rather, these properties resemble those of long GRBs. Its other observational properties such as its spectral behaviours, total energy and host galaxy offset are, however, inconsistent with those of other short GRBs believed to originate from binary neutron star mergers. Characterized by a sharp pulse, this burst shows a duration of 1 second and no evidence of an underlying longer-duration event. Here, we report the comprehensive analysis of the multi-wavelength data of the short, bright GRB 200826A. Some apparently long GRBs have been suggested to have a neutron star merger origin5, whereas some apparently short GRBs have been attributed to genuinely long GRBs6 whose short, bright emission is slightly above the detector’s sensitivity threshold. It has been known that the duration criterion is sometimes unreliable, and multi-wavelength criteria are needed to identify the physical origin of a particular GRB4. Multi-wavelength and multi-messenger observations in recent years have revealed that in general long GRBs originate from massive star core collapse events2, whereas short GRBs originate from binary neutron star mergers3. Gamma-ray bursts (GRBs) have been phenomenologically classified into long and short populations based on the observed bimodal distribution of duration1. By performing a Monte-Carlo fit to the observational spectra of GRB 200415A, we found that the observation of the burst is entirely consistent with our model predictions. The model predicts a modified thermal-like spectrum characterized by a low-energy component in the Rayleigh-Jeans regime, a smooth component affected by coherent Compton scattering in the intermediate energy range, and a high-energy tail due to the inverse Compton process. ![]() Magnetars, a population of isolated neutron stars with ultra-strong magnetic fields of $\sim 10^$ pairs in the magnetar wind region, which produces additional higher-energy gamma-ray emission. We then implemented the LIV effect into the fit, which enabled us to constrain the lower limit of the linear and quadratic values of E QG, which are typically distributed at 1.5 × 10 ¹⁴ and 8 × 10 ⁵ GeV, respectively. We first fit each of the lag– E relations of the 32 GRBs with an empirical smoothly broken power-law function, and found that the lag transition occurs typically at about 400 keV. This search resulted in 32 GRBs with redshift available, which exhibit the lag transition phenomenon. Motivated by previous case studies, this paper systematically examined the up-to-date GRB sample observed by Fermi Gamma-ray Burst Monitor for the lag transition feature to establish a comprehensive physical limit on the Lorentz invariance violation (LIV). An application of such a feature has been made to constrain the critical quantum gravity energy ( E QG ) of the light photons under the hypothesis that the Lorentz invariance might be violated. The positive-to-negative transition of spectral lag is an uncommon feature reported in a small number of gamma-ray bursts (GRBs).
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