Spin Evolution Of Accreting Neutron Stars

Neutron Stars(NSs)are the most compact object in the universe eccept for black holes(BHs)and the accretion onto them is an important field in astronomy which has many observations.The pulse period is one of the characteristics that distinguish NSs from BHs and other objects,which is dominated by the interaction between the magnetic field and the environment in most systems.In general,there are three kinds of NS-systems:the low-mass X-ray binaries(LMXBs),the highmass X-ray binaries(HMXBs)and the isolated NSs.In LMXBs,the disk is ease to form arond the NS because the donar star transfer mass via Roche Lobe(RL),so the classical thin disk accretion theory fits.While in HMXBs(except for Be-NS sytems),the accretion is domianted by star wind because the mass loss rate of the companion star with RL unfilled is usually high and the mass transfer rate is too low to shape a disk.In the young isolated NS systems,a disk can form if part of ejected material gravitationally captured by the newborn NS after the supernova(SN)explosion,then the fallback disk accretion acts on the NS.I study the three kinds of NS-systems and accretion theories in the work.Firstly in chapter 1,I introduce the birth,the environment,the interaction with the environment and the kinds of the NSs.Then I discuss the accretion therioes and the spin evolution of the NSs in the different systems,as well as some qustions including magnetars,ultra-luminous X-ray pulsars(ULXPs)and the spin evolution of long period NSs.In the second chapter,I settles the accretion disk model of the first ULXP M82 X-2 and estimates its magnetic field.ULXs are the X-ray sources with Lx>1039 erg s-,which were thought to be intermidiate mass black holes when discovered.But a pulse period of M82 X-2 was found,which indicaates its a NS.Then there are many debates on its magnetic field and we used thin disk model and thick disk model to adapt the changing trend of its accretion rate as well as reckoning its field?013 Gauss,which is consistent with the age of M82 X-2.The third chapter shows the evolution of the slowest isolated pulsar 1E 161348-5055,which is located close to the center of the supernova remnant RCW 103 with an age?2000-4000 yr.The spin period is?6.67 h(?24000 s),and there is no counterpart in the radio or optical observed,casting doubt on a binary nature.Observations of outbursts from 1E 1613 and the evolution of the spectral and timing properties along the outburst decay reveal it to be a magnetar.So the problem in the magnetar scenario is how to spin down the NS from a birth period?0.01-1 s to about 24 000 s via magneto-dipole radiation within a few thousand years.Therefore a SN fallback disk is required to provide additional torque in the propeller stage.We use the fallback disk model to explain the source and suggest that a magnetar with magnetic field>5 × 1015 G and a initial disk mass?10-7M? could slow down to 6.67 h in about 4000 yr.And the parameter space is very small,which verified that 1E 1613 is a very special source.Finally in the fourth chapter,I summarize the above works the first section.Then the work in process of how to find the magnetars from HMXBs is showed in the second section.I discuss the accretion regimes of the HMXBs and show the preliminary results got by now.Using the binary-star evolution(BSE)code and my NSs spin evolution code to perform a group of parameters and the results show that it's promising to distinguish the magnetars from normal NSs.In the third section I discuus the future works.