Physics of Gamma-Ray Bursts Prompt Emission

Figure 8

Full width half maximum of the spectral peaks of over 2900 bursts fitted with the “Band” function. The narrow most spectra are compatible with a “Planck” spectrum. About ~80% of the spectra are too narrow to be fitted with the (slow cooling) synchrotron emission model (red line). When fast cooling is added, nearly 100% of the spectra are too narrow to be compatible with this model. As it is physically impossible to narrow the broadband synchrotron spectra, these results thus suggest that the spectral peak is due to some widening mechanism of the Planck spectrum, which are therefore pronounced (indirectly) in the vast majority of spectra. Figure taken from Axelsson and Borgonovo [109].