银河系隆起中周期性X射线源：Gregory-Loredo算法的应用
Periodic X-ray Sources in the Galactic Bulge: Application of the Gregory-Loredo Algorithm
摘要：
我们提出了一个系统的研究周期性X射线源的限制窗口（LW），一个$\sim$ 70 arcmin的$^2$领域的代表内银河系的隆起和目标的$\sim$ 1毫秒钱德拉观测。采用适合于不规则采样X射线数据的Gregory-Loredo算法，在23个离散源中检测到25个周期信号，其中15个信号是新发现的，两个源显示出双周期。根据它们的周期范围、X射线亮度、光谱特性和具有自旋调制特征的相位折叠光变曲线，23个周期源中的绝大多数被归类为磁激变变星（CV）。同时，存在被视为周期性源的非磁性CV的缺乏，这可以理解为是由于对食源的低检测效率。在合理的假设下的几何形状的磁CV和一个大的模拟X射线光变曲线，我们估计的比例磁CV在银河系内部的隆起是$\lesssim$ 23%，这是类似于在太阳附近。与太阳附近已知的CV范围相比，LW中明显缺乏长周期（$\gtrsim$ 3.3小时）CV。我们认为，这可能是一个年龄的影响，在这个意义上说，CV的内部隆起是更先进的系统，并大大缩小了他们的轨道。
英文摘要：
We present a systematic study of periodic X-ray sources in the Limiting Window (LW), a $\sim$70 arcmin$^2$ field representative of the inner Galactic bulge and the target of $\sim$1 Ms Chandra observations. Using the Gregory-Loredo algorithm, which applies Bayes's theorem to the phase-folded light curve and is well-suited for irregularly sampled X-ray data, we detect 25 periodic signals in 23 discrete sources, among which 15 signals are new discoveries and two sources show dual periods. The vast majority of the 23 periodic sources are classified as magnetic cataclysmic variables (CVs), based on their period range, X-ray luminosities, spectral properties, and phase-folded light curves that are characteristic of spin modulation. Meanwhile, there is a paucity of non-magnetic CVs seen as periodic sources, which can be understood as due to a low detection efficiency for eclipsing sources. Under reasonable assumptions about the geometry of magnetic CVs and a large set of simulated X-ray light curves, we estimate the fraction of magnetic CVs in the inner Galactic bulge to be $\lesssim$23%, which is similar to that in the solar neighborhood. There is an apparent lack of long-period ($\gtrsim$3.3 hours) CVs in the LW, when contrasted with the range of known CVs in the solar neighborhood. We suggest that this might be an age effect, in the sense that CVs in the inner bulge are more evolved systems and have substantially shrunk their orbits.
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