标题： BeppoSAX 对附近低质量 X 射线双星和快速暂现源 SAX J1819.3-2525 的观测 显示英文标题

标题： BeppoSAX observations of the nearby low-mass X-ray binary and fast transient SAX J1819.3-2525

摘要： 1RXS J181936.7−252525 是一颗附近的 X 射线暂现源，在 1999 年 9 月 15 日发生了一次快速且强烈的 X 射线爆发（Smith 等人，1999 年）。BeppoSAX 卫星上的宽视场相机和窄视场仪器（NFI）在此之前于 1999 年春季和秋季观察到了 SAX J1819.3-2525 在其活动的不同阶段。这些观测的流量范围在 0.012 到 0.3 蟹状星云单位之间（2-10 keV）。NFI 观测的独特之处在于这是迄今为止 SAX J1819.3-2525 最长的半连续观测，并提供了相对较高的光谱分辨率（6 keV 处半高全宽为 8%）的研究机会。 我们重点讨论了 X 射线光谱的观测结果。在 SAX J1819.3-2525 中检测到一个强度很强的 Fe-K 发射线，其等效宽度在 0.3 到 1 keV 之间。该线的能量高达 6.85 ± 0.02 keV，表明存在高度电离的铁。我们认为这是由光电离等离子体产生的荧光发射。连续谱的光谱特征与低质量 X 射线双星一致，其中吸积盘冕的辐射起重要作用。尽管在无线电波段看到的双喷流暗示了一个高倾角，但在这一曝光中没有发现由于双星轨道引起的掩食或周期信号。 显示英文摘要

摘要： SAX J1819.3-2525 is a nearby X-ray transient which exhibited a fast and large X-ray outburst on Sep. 15, 1999 (Smith et al. 1999). The Wide Field Cameras and the Narrow Field Instruments (NFI) on board BeppoSAX observed SAX J1819.3-2525 at various stages of its activity before that, in the spring and fall of 1999. The fluxes range between 0.012 and 0.3 Crab units (2-10 keV). The NFI observation is unique because it is the longest semi-continuous observation of SAX J1819.3-2525 so far, and it offers a study of the spectrum at a relatively high resolution of 8% full width at half maximum at 6 keV. We discuss the observations with emphasis on the X-ray spectrum. A strong Fe-K emission line was detected in SAX J1819.3-2525 with an equivalent width between 0.3 and 1 keV. The line energy is up to 6.85 +/- 0.02 keV and suggests the presence of highly ionized iron. We identify this as fluorescent emission from a photo-ionized plasma. The continuum spectrum is typical for a low-mass X-ray binary in which emission from an accretion disk corona plays an important role. There is no sign of an eclipse or periodic signal due to the binary orbit in this exposure, despite the fact that the twin jets seen at radio wavelengths suggest a high inclination angle.