Comparison Of Gravitational Waves From Three Kinds Of Central Engines Of Gamma-Ray Bursts

Gamma-ray bursts(GRBs)were discovered accidentally in 1970s.It is a transient astronomical phenomenon that gamma-ray radiation increases rapidly in a short time.Since the discovery,the GRB has become an active research field in astronomy.As-tronomers believe that GRBs are events in cosmological distances.There are two key problems around the GRBs:one is the radiation mechanism of the GRBs,that is,how the GRBs change the energy into the radiation of each band,the other is the central energy mechanism of the GRBs,that is,the essence of the progenitors of GRBs and why they can release such a huge energy(the "central engine").For the first problem,the mainstream view of astronomers is the "fireball-shock model",and for the second problem,it is generally believed that the long GRBs originate from the collapse of massive stars,and the short GRBs originate from the merger of compact stars(neu-tron star-neutron star merger or black hole-neutron star merger).There are three main models for the central engines of GRBs,namely,neutrino-dominated accretion flows(NDAF),Blandford-Znajek mechanism(BZ mechanism)and magnetars.These three models have different capabilities to explain different GRBs.How to distinguish the type of central engine of a GRB is the object of our study.This thesis calculates the strain and power of the gravitational waves emitted by a GRB more accurately.We suggest that the type of the central engine of a GRB can be judged by observing the gravitational waves emitted by the GRB.In the first chapter to the third chapter,we introduce basic background knowledge related to GRBs and gravitational waves:In the first chapter,we introduce the GRBs,including its observational history,properties and two key problems about the GRBs:the radiation mechanism and the central energy mechanism.We point out that the problem of radiation mechanism can be explained by the "fireball-shock model" and we also introduce the progenitors of the GRBs.In the second chapter,we introduce the theory of black hole accretion disks,in-cluding black holes’ theoretical research history,properties,formation process,struc-ture,classification and observation evidence.Then we introduce the concept and types of accretion disks.Finally,we introduce three kinds of central engine models to be distinguished in this thesis:NDAFs,BZ mechanism and magnetars.In the third chapter,we introduce gravitational waves,including its research his-tory,properties,generation,detection methods,detectors and history of discovery.In the fourth chapter and the fifth chapter,we discuss our research achievements.In the fourth chapter,we calculate the gravitational waves emitted by NDAFs more accurately.We calculate the relationships between gravitational waves’ strain h and black hole spin a*,accretion rate m,distance D.We also calculate the quadrupole power Pquad of gravitational waves.These calculations are of great significance for gravitational wave detection in the future.In the fifth chapter,we compare the gravitational waves generated by NDAFs with gravitational waves generated by the BZ mechanism and the magnetars.We propose a method to distinguish the central engine of a GRB by detecting its gravitational wave.We present the detection distance of the three models under aLIGO and ET.Our conclu-sion is that the gravitational waves can be used to distinguish the central engine model of the GRBs.Finally,we briefly look forward to the future research plan.