Constrains On Gamma-Ray Burst Central Engine Models From Multi-Band Data Analysis And Statistical Studies

Gamma-ray bursts(GRBs),transient gamma rays from the sky,are currently the most luminous explosions in the universe.After its discovery in 1973,GRB has attracted more and more attentions due to its special properties,such as high energy,high redshift,and rich multi-band data.Great interest has been paid to the physics of GRB,as well as using it as a tool for cosmology studies.In this thesis,I mainly focus on the research of central engine of GRB with its large collections of data.I introduce the progress of GRB studies in the first chapter on both observations and theories,including the history,the observational results in different eras,the current GRB satellites and the GRB networks,the fireball model,the progenitors of GRBs,the central engines,the standard model for afterglows and the post-standard effects,the internal dissipation for afterglow plateaus,the kilonova mechanisms,etc.In the second chapter,I present my first work on constraining the central engine models with the GRB multi-band data.If magnetars are the central engines of some GRBs,then several evolutionary results of magnetars are expected:(1)the immediate collapse into a black hole(BH);(2)the collapse of a supra-massive magnetar into a BH after it spins down;and(3)a stable magnetar.From GRB samples,we find two candidates exhibiting evidence of a magnetar central engine at early afterglow and a newborn starving BH at late time.Our results suggest that some magnetars may indeed collapse into a BH,which provides direct support for the magnetar and BH central engine models.In the third chapter,I show that the scenario presented in chapter two may work in the recent gravitational wave(GW)event GW170817/GRB 170817A/ AT2017 gfo.The latest observations on GRB 170817 A exhibited unexpected re-brightening at late time in both Xray and radio emissions.A residual component,revealed by our spectral fit to the optical data in AT2017 gfo with kilonova model,is likely non-thermal afterglow emission and demonstrates the similar rising behavior.We propose that these re-brightening emissions could be powered by the newborn BH from the collapse of a supra-massive magnetar.To check this scenario,we perform MCMC fit to the X-ray,radio and the residual optical data with our model.In chapter four,I try to constrain the central engine models based on the statistical analysis of large GRB sample.As the first step,I develop Capella,an automatic data collection and statistical analysis code dedicated for GRB studies.We then collect large amounts of GRB data with Capella from all available public data archive.We finally perform comprehensive statistical studies on the GRB sample.We put special focus on the central engine of ultra-long GRBs.The fifth chapter presents a summary of my work,the limitations of our model,and some prospects on GRB study.