Investigating The Synchrotron Radiation In The Prompt Emission Spectra Of Fermi Gamma-ray Bursts

Gamma ray burst?GRB?is a short-time gamma ray burst phenomenon in the universe.Since it was discovered in 1967,it has been a research hotspot in astrophysics.Through the study of the GRB spectrum,the energy,magnetic field,acceleration mechanism and other information of its burst can be obtained.These are particularly important for us to understand the nature of GRBs.This paper uses a parameter?curvature width W?that can measure the spectral break sharpness of the GRB energy spectrum to verify the consistency of the synchrotion model and the GRB energy spectrum.We first calculate the curvature widths of several typical synchrotion spectra such as single electron,single power law energy distribution and break power law energy distribution.Then select a Fermi/GBM long burst time-resolved energy spectrum sample containing 1198 spectra.The sample is obtained by fitting the GRB data with the empirical model and calculating the curvature width of the sample spectrum.By comparing these two widths,it is found that most of the energy spectrum is inconsistent with the synchrotion model,because the spectrum break of the synchrotion spectrum is smoother than the data.Even for some bursts,the theoretical model and the observed data have the same curvature width.The smooth spectral break of the synchrotion model implies that the two types of energy spectra are inconsistent.The above results show that the synchrotion model is difficult to explain most of the GRB energy spectrum.In addition,considering the evolution of the energy spectrum,it is found that there is a weak inverse correlation between the photon flux and the curvature width in the single pulse of the burst,indicating that the higher the flux,the sharper the spectral break and the more deviation from the synchrotion model.We also use two energy spectrum fitting methods to further verify the sharp spectral break of the data:?1?Use the synchrotion model to fit the time-resolved data of GRB100826 and GRB170826B,and find that the synchrotion model is under the high energy cutoff?high energy index p₂ very large?fits these two bursts well;in addition,the spectral width and spectral sharpness angle defined by the predecessors?Magnus Axelsson and Yu Hoi-Fung?are calculated and compared with the synchrotion spectrum,the synchrotion model cannot explain most of the spectrum.?2?Use three models SBPL?smooth break power law?,BPL?power law connected polyline model?and Band to fit 8 bright bursts,and obtain darker bursts that can be fitted well with BPL and the best fitting model for nearly half of the energy spectrum in the sample is BPL,and the brighter bursts can be fitted well with SBPL and Band,indicating that the spectral shape of some darker bursts is close to the polyline shape;We also get the existing data that cannot distinguish these photon models well;in addition,the current fitting is affected by the instrument response matrix,and the true physical model cannot be well determined,that is,the GRB spectrum seems to be explained by the model,but may not be true.Both methods show that the observed data spectrum has sharp break,so that synchrotion cannot explain most of the observed spectrum.Our results show that the synchrotion model cannot fully explain the GRB energy spectrum.The spectrum break of the synchrotion spectrum is smoother than the data.In addition to the synchrotion mechanism,the addition of other radiation mechanisms is required to fully explain the GRB prompt emission energy spectrum.Finally,we summarize this article and list some other problems that need to be solved in the prompt emission of GRBs.