标题： 与4U 1626-67流量增强相关的光谱和时间变化 显示英文标题

标题： Spectral and temporal changes associated with flux enhancement in 4U 1626-67

摘要： 4U 1626-67 是一个吸积驱动的X射线脉冲星，在小时量级时间尺度上表现出显著稳定的X射线光度，并在几年量级时间尺度上出现渐进的强度变化。在这里，我们报告了在4U 1626-67长期RXTE-ASM光变曲线中X射线强度的显著增加。类似地，Swift-BAT光变曲线中也检测到了X射线通量的增强。X射线通量的增加持续了一个大约100天的长时间段，并且似乎出现了两次通量增强事件。我们利用罗西X射线时变探测器上的比例计数器阵列和高能X射线时变探测器获得的数据，研究了4U 1626-67在当前增强通量发射状态下的光谱和定时特征。该源进入了新的自转加速阶段，自转加速率为4.02(5) $\times$ 10$^{-13}$ Hz s$^{-1}$。目前的自转加速率几乎是先前自转加速和减速趋势的一半。在增强通量状态下观察到了软X射线光子发射的显著过量，这与脉冲星在1990年前自转加速时期的能量谱相似。我们还报告了在130 mHz峰的翼部出现了显著的展宽以及功率谱连续谱形状的变化。 显示英文摘要

摘要： 4U 1626-67 is an accretion powered X-ray pulsar that shows remarkably stable X-ray luminosity above hours timescale and gradual intensity variation on a few years timescale. Here we report a significant increase in the X-ray intensity in the long term RXTE-ASM light curve of 4U 1626-67. Similar enhancement in the X-ray flux has also been detected in the Swift-BAT light curve. The increase in the X-ray flux took place over a long period of about 100 days and there appears to be two episodes of flux enhancement. We have investigated the spectral and timing features of 4U 1626-67 during its current state of enhanced flux emission with data obtained from the Proportional Counter Array and the High-Energy X-ray Timing Explorer on board the Rossi X-ray Timing Explorer. The source has entered a new spin-up phase with a spin-up rate of 4.02(5) $\times$ 10$^{-13}$ Hz s$^{-1}$. The present spin-up rate is almost half of the earlier spin-up and spin-down trends. A significant excess in soft X-ray photon emission is observed during the enhanced flux state, which is similar to the energy spectrum obtained during the spin-up era of the pulsar before 1990. We also report detection of a significant broadening in the wings of the 130 mHz peak and a change in the shape of the continuum of the power spectrum.