A Connection between Spectral Width and Energetics As Well As Peak Luminosity in Fermi Gamma-Ray Bursts

TL;DR

This study investigates the spectral width of gamma-ray bursts, revealing correlations with energetics and peak luminosity, and challenges simple emission models like blackbody and synchrotron radiation.

Contribution

It demonstrates positive correlations between spectral width and burst properties, including energy and luminosity, extending to short bursts and in the cosmological rest frame.

Findings

Spectral width correlates with isotropic energy and luminosity.

Blackbody emission cannot explain observed spectra.

Short bursts extend the spectral property trends.

Abstract

We have revisited the spectral width in the EF E spectrum of gamma-ray bursts with the BEST peak flux P and time-integrated F spectral data provided by the Fermi GBM Burst Catalog. We first compute the BEST spectral widths to compare with some typical physics models. Our analysis results consist with the previous results: blackbody emission alone cannot explain the observed spectrum and most of the observed spectra cannot be interpreted by the synchrotron radiation. We then check the correlations between the spectral width and the observable model-independent burst properties of duration, fluence, and peak flux and find that positive correlations exist between them for both the P and F spectra. Moreover, the short burst appears to extend the correlation found for the long burst. We further demonstrate that these positive correlations also exist in the cosmological rest frame; that is, the spectral width correlates with the isotropic-equivalent energy E iso as well as the isotropic-equivalent peak luminosity L iso for different energy bands and timescales. Our results show that the wider bursts have larger energy and luminosity. Moreover, short bursts would appear to extend this trend qualitatively. Taking the Amati relation into account, we tend to believe that the spectral shape is related to energy and luminosity.