| Neutron stars are one of the evolutionary outcomes of massive stars after supernova explosions.Neutron stars have unique physical properties（high temperature,high pressure,strong magnetic field and fast rotation）.They are natural laboratories for studying extreme physical conditions,which have a profound impaction on the development of modern physics.Observation and research on neutron stars can help us understand the formation and evolution of pulsars,as well as the physical properties of precursors.Pulsating ultraluminous X-ray sources are a special class of pulsars,it’s located in high-mass X-ray binary systems with luminosity exceeding the Eddington limit.The identification of pulsating ultraluminous X-ray sources broke people’s previous understanding of pulsating ultraluminous X-ray sources and provided a new way to study the PULXs.There is no unified conclusion about the reason for its ultra-high luminosity and how the specific radiation mechanism is formed,but scholars have studied that this feature may be related to the magnetic field strength of the star,so we will focus on the second PULX:NGC 7793 P13.Observations show that the source has bright X-ray luminosity,stable pulse,and it far away from other sources in the galaxy group,so it is easy to distinguish.By calculating the magnetic field strength of this source and simulating its evolution,we will explain its properties and evolution characteristics.The structure of the thesis is divided into four parts.In the first chapter,we introduce the basic properties of neutron stars.Including the discovery history of neutron stars,neutron stars’models,structures and classification;and introduce a special kind of neutron star,magnetars.Magnetars are a class of neutron stars with strong magnetic fields,and are associated with some physical activities of stellars.The second chapter is a brief introduction to the 12 pulsating ultraluminous X-ray sources that have been certified so far,such as observation time,observation luminosity,rotation period and spin-up rate.Studies have shown that magnetars may be related to the pulsating ultraluminous X-ray source,and the multipolar magnetic field structure of magnetars can explain the physical properties of such sources have higher luminosity than Eddition limit.In the third chapter,we studied the magnetic field and evolution of NGC 7793P13.With the observation data of this source by Nu STAR and XMM-Newton,we calculated the magnetic field strength of NGC 7793 P13 is B～1012G through the relationship between the spin-up rate with the magnetic field and luminosity during the accretion phase.Then we simulate the magnetic field evolution by the accretion induced dipole magnetic field decay model,it is found that the initial magnetic field of the source can reach 4×1014G,it may be a magnetar.The source may have a multipole magnetic field structure,which will suppress the scattering cross section of the electron,making its luminosity exceed the Eddington limit.In the simulation,it is found that the source evolves to the current magnetic field strength after about 104yrs.Due to the influence of the mass of the companion star,the star eventually evolves into a recycled pulsar with a magnetic field strength of B～（3.7-5.0）×109G and period of about a few hundred milliseconds.Chapter 4 is the summary. |
