Gamma Ray Bursts in the Fermi era: the spectral energy distribution of the prompt emission

TL;DR

This paper introduces a log-parabolic model for GRB spectral energy distributions, which is statistically favored over the traditional Band function and is motivated by theoretical acceleration scenarios, with Fermi data being key for validation.

Contribution

It proposes a new log-parabolic spectral model for GRBs that is simpler and theoretically motivated, challenging the traditional Band function.

Findings

Log-parabolic model fits GRB spectra with fewer parameters.

The model is statistically favored over the Band function.

Fermi observations are essential to distinguish between models.

Abstract

Gamma Ray Bursts (GRBs) show evidence of different light curves, duration, afterglows, host galaxies and they explode within a wide redshift range. However, their spectral energy distributions (SEDs) appear to be very similar showing a curved shape. Band et al. (1993) proposed a phenomenological description of the integrated spectral shape for the GRB prompt emission, the so called Band function. In this letter we suggest an alternative scenario to explain the curved shape of GRB SEDs: the log-parabolic model. In comparison with the Band spectral shape our model is statistically favored because it fits the GRB spectra with one parameter less than the Band function and it is motivated by a theoretical acceleration scenario. The new Fermi observations of GRBs will be crucial to disentangle between these two models.