Studies of Accretion Flow onto a Neutron Star

我们研究了低质量双星X射线强度的能谱性质和准周期振荡(QPO)。我们已经进行了一项调查，在理论和观察之间进行了密切的相互作用。我们从Ginga观测中获得了以下重要结果：(1)发现了水平分支QPO与低频噪声之间的不相关变化；(2)探测到了Cen X-3和4U 1626-67 X射线脉冲星的QPO；(3)发现了4U 1608-522能谱7-20keV范围内的浅而宽吸收特征；(4)从X射线瞬变GS 1124-68探测到了2-6 Hz QPO。(2)X射线脉冲星的QPO可以解释为拍频强度调制。(3)能谱中的浅宽吸收结构可能是由于部分X射线从中子星表面反射到盘的外部。(4)GS 1124-68观测到的低频QPO可能是由于吸积盘中激发的波所致。我们的研究为我们理解中子星吸积流提供了重要的基础。需要做更多的研究来阐明吸积流的详细性质。

We have studied the energy spectral properties and quasi-periodic oscillations (QPO) of X-ray intensities especially from the low mass binary X-ray stars. We have proceeded an investigation performing an intimate interplay between theory and observation. We have obtained the following important results from Ginga observations :(1) a discovery of noncorrelated variation in power between the horizontal branch QPO and the low frequency noise(2) detectins of QPOs from X-ray pulsars Cen X-3 and 4U 1626-67(3) a discovery of a shallow and broad absorption feature in the 7-20 keV range of the energy spectrum of 4U 1608-522(4) a detection of 2-6 Hz QPOs from X-ray transient GS 1124-68The main results of theoretical studies are summarized as follows :(1) Conducting a shot noise simulation, we found that the plasma clump-magnetic field interaction used in the beat frequency model cannot explain the observed fact (1).(2) QPO of X-ray pulsars may be interpreted as a beat frequency intensity modulation.(3) A shallow broad absorption structure in the energy spectra may be due to the reflection of a part of X-rays from the neutron star surface in the outer part of the disk.(4) The low frequency QPOs as observed from GS 1124-68 may be due to the waves excited in the accretion disk.Our studies here provided us with an important basis to understand the accretion flow onto a neutron star. More studies should be done to elucidate the detailed properties of the accretion flow.