The Spectrum Component Evolution In Gamma-Ray Burst Prompt Emission And The Restrictions Of Fireball Model

The research object of this paper is the sudden brightening of gamma ray in the universe,called gamma-ray burst.The prompt emission of gamma-ray burst can well reflect the activity of central engine.This paper focuses on the evolution of the emission components in the spectrum and the limitation of related features on the fireball modelIn chapter 2,GRBs are studied by jointing data from China's first space astronomical satellite Hard X-ray Modulation Telescope(HXMT)and other satellites.In the first section,we joint the data of HXMT,Swift and Fermi,and discuss the feasibility and advantages as well as disadvantages of using HXMT to study GRBs through the light curve and spectrum.In the second section,taking GRB 181225A as an example,we joint HXMT and Fermi data for spectrum analysis,and find that the energy spectrum has obvious spectrum evolution behavior,and the spectrum changes from thermal to non-thermal.The identification of the emission from the photosphere allows us to constrain several important physical parameters by assuming that the redshift is the typical value(z=1)In chapter 3,the spectrum components of prompt emission and the limitations of fireball parameters are further explored by utilizing Fermi data.In the first section,38 GRBs are jointly detected by Fermi GBM and LAT are selected as samples and their spectrum fitting parameters are systematically analyzed.Considering the observed effects and various physical processes,the photospheric component is better represented by a multicolor blackbody(mBB)instead of a single Planck function,and non-thermal components are described by a power law(PL)or cutoff power law(CPL)function,which verifies that the"Band" component comes from the quasi-thermal components of the photospheric layer.In the second section,the Lorentz factor of fireball is restricted by empirical relationship and its evolution in the prompt emission of multipulse GRBs is studied.We select 6 GRBs with distinct independent pulses and redshift observations.The model parameters obtained by energy spectrum analysis are used to estimate the evolution of Lorentz factors by considering a tight Lp,iso,52-Ep,z-?O correlation.In this paper,the contribution of HXMT to GRBs observation is described,the evolution of prompt emission spectrum is analyzed by means of multiple instruments and the parameters of the fireball model are studied and discussed.