Study On Energy Injection And Jet Structure In The Afterglow Of Gamma-Ray Bursts

This paper focuses on the afterglow of gamma-ray bursts(GRBs),including the energy injection behavior and jet structure.Firstly,we mainly studied the energy injection behavior of the external-forward shock in GRBs with multiple outbursts in the central engine,including the injection time and injection form.In the study of energy injection time,we found that the energy injection time(tb)depends on the Lorentz factor(?jet,2)of late jets and the interstellar medium density(n).If the Lorentz factor of late jets or the interstellar medium density is significantly high,the time of energy injection in the external shock approximately equals to the observed time of late jets'emission(tjet).If the Lorentz factor of late jets and the interstellar medium density are significantly low,the time of the energy injection lags behind tjet significantly.Based on the above results,we estimate the Lorentz factor of main burst in GRB160625B.The Lorentz factor of the main burst is about 107 in the case of stellar wind and about 220 in the case of interstellar medium.In addition,we take GRB111209A as an example to discuss the form of its energy injection.By taking the X-ray light-curve evolution as the form of energy injection,the optical light curve of GRB111209A can be fitted well.Secondly,we explore the structures of jet under the assumption of existing a uniform-precession jet.We calculated the final structure of jet by a Monte Carlo method.The final structure of the jet depends on the precession angle.If the jet power is constant during precession,the power law,Gaussian and annular jet structures are obtained.If the jet power evolves with time in the precession process,then,the obtained jet structure is extremely complex,showing the non-axial symmetry.