Study Of The Millihertz Quasi-periodic Oscillations In Low-mass X-ray Binary

The millihertz quasi periodic oscillation signal(m Hz QPO)originates from the marginally stable nuclear burning on the surface of the neutron stars.Therefore,the study of m Hz QPO plays an important role in understanding the nuclear burning process and related physics on the neutron star surface.In this thesis,we study the quality factor Q and coherence time in the m Hz QPOs in the neutron-star low mass X-ray binary 4U 1636-53,and further study the thermal radiation properties on the neutron star surface.With the RXTE observations,we found that the quality factor Q of the m Hz QPOs is relatively small,ranging from～3-9.In addition,we found that the frequency and the root mean square(rms)amplitude of the m Hz QPOs are not significantly correlated with the quality factor Q.And our results show that there is no obvious correlation between the factor Q and the parameter S_a.This result could be explained if it is the local mass accretion rate that triggers the m Hz QPOs.In addition,we studied the thermal radiation on the neutron star surface in the period of m Hz QPO in 4U 1636-53 with one XMM-Newton observation.We analyzed the energy spectrum before and after the emergence of the m Hz QPO,and compared our results with the one predicted by the theoretical model.We found that the temperature of the blackbody component before the m Hz QPO is 1.94±0.01 ke V,and the temperature after the emergence of MHz QPO is 1.89±0.01 ke V.The thermal radiation flux of the neutron star surface becomes lower when the m Hz QPO appears.This result is not completely consistent with the one from the model.One possible reason is that the local accretion rate in the burning area before the appearance of the QPO may be higher than the value selected in the theoretical model.Besides,we found that the area of the burning region becomes larger when the m Hz QPO appears.The structure of this paper is as follows:The first chapter introduces the classification and characteristics of binaries,and we also show the structure and the properties of neutron stars.The second chapter introduces the classification and characteristics of the QPOs.The third chapter introduces the classification and the characteristics of X-ray telescopes.The fourth chapter shows the research methods and the tools for studying the m Hz QPOs in low mass X-ray binaries.The fifth chapter introduces the research in the quality factor Q and the coherence time of the m Hz QPOs.The sixth chapter shows the research in the surface thermal radiation of the neutron star during m Hz QPO period in 4U 1636-53.