论文标题
在最低观察到的BE/X射线二元脉冲星Exo 2030+375的X射线脉动的检测中
Detection of X-ray pulsations at the lowest observed luminosity of Be/X-ray binary pulsar EXO 2030+375 with AstroSat
论文作者
论文摘要
我们使用与Astrosat的较大面积氙气比例计数器和软X射线望远镜的观测观察到BE/X射线二元二元二元二元二元exo 2030+375获得的结果，在2016年，2018年和2020年的观察过程中，在其类型I型爆发的各个阶段，Astrosat的各个阶段。以2.5 $ \ times $ 10 $^{35} $ erg s $^{ - 1} $在0.5---30 kev Energy范围内，$ \ $ \ $ 41.3 s的脉动在X射线光曲线中清楚地检测到。这一发现建立了迄今为止以极低的质量积聚率，在Exo 2030+375中首次对脉动的脉冲检测。由于存在几个狭窄的倾角，脉冲轮廓的形状很复杂。尽管在源更明亮时发现了脉动最多可达$ \ sim $ 80 kev，但在第三次Astrosat观察期间，以最低的源亮度为单位，脉动被限制为$ \ sim $ 25 kev。在2 $ \ times $ 10 $^{ - 4} $ hz至10 Hz中搜索准周期性振荡，产生了负结果。 Astrosat数据的光谱分析表明，Pulsar的光谱陡峭，幂律指数为$ \ sim $ 2。在观察到的低亮度下，光子迹象的值遵循脉冲星的亚临界方向的已知模式。
We present the results obtained from timing and spectral studies of Be/X-ray binary pulsar EXO 2030+375 using observations with the Large Area Xenon Proportional Counters and Soft X-ray Telescope of AstroSat, at various phases of its Type-I outbursts in 2016, 2018, and 2020. The pulsar was faint during these observations as compared to earlier observations with other observatories. At the lowest luminosity of 2.5$\times$10$^{35}$ erg s$^{-1}$ in 0.5--30 keV energy range, $\approx$41.3 s pulsations were clearly detected in the X-ray light curves. This finding establishes the first firm detection of pulsations in EXO 2030+375 at an extremely low mass accretion rate to date. The shape of the pulse profiles is complex due to the presence of several narrow dips. Though pulsations were detected up to $\sim$80 keV when the source was brighter, pulsations were limited up to $\sim$25 keV during the third AstroSat observation at lowest source luminosity. A search for quasi-periodic oscillations in 2$\times$10$^{-4}$ Hz to 10 Hz yielded a negative result. Spectral analysis of the AstroSat data showed that the spectrum of the pulsar was steep with a power-law index of $\sim$2. The values of photon-indices at observed low luminosities follow the known pattern in sub-critical regime of the pulsar.
