朱雀共生系统SS73 17
The Symbiotic System SS73 17 Seen with Suzaku
摘要：
我们与朱雀一起观察了共生恒星SS 73 17，这是由于INTEGRAL卫星和Swift BAT调查发现它发射硬X射线。我们的观测结果显示，虽然该源的B星等为11.3等，并且在紫外线下也很亮，但它的X射线光谱具有高吸收性，NH > 10^23 cm-2，相当于A_V > 26。该源还显示出强的窄铁线，包括荧光Fe K以及Fe XXV和Fe XXVI。X射线光谱可以与包括部分覆盖源的吸收分量的热模型拟合。在这个模型中，铁荧光线的大部分等效宽度可以解释为在致密吸收体中的再加工加上白矮星表面的反射，但很可能连续谱也部分地在反射中看到。与其他显示硬X射线发射的共生系统（CH Cyg，RT Cru，T CrB，GX 1 +4）不同，SS 73 17没有显示出类似新星的光学变化，X射线闪光或脉动，并且总是显示微弱的软X射线发射。因此，虽然它很可能是一颗白矮星，但SS 73 17中致密天体的性质仍然不确定。SS 73 17可能是最近发现的一类相对较小的硬X射线发射共生系统的极端例子。
英文摘要：
We observed with Suzaku the symbiotic star SS73 17, motivated by the discovery by the INTEGRAL satellite and the Swift BAT survey that it emits hard X-rays. Our observations showed a highly-absorbed X-ray spectrum with NH > 10^23 cm-2, equivalent to A_V > 26, although the source has B magnitude 11.3 and is also bright in UV. The source also shows strong, narrow iron lines including fluorescent Fe K as well as Fe xxv and Fe xxvi. The X-ray spectrum can be fit with a thermal model including an absorption component that partially covers the source. Most of the equivalent width of the iron fluorescent line in this model can be explained as a combination of reprocessing in a dense absorber plus reflection off a white dwarf surface, but it is likely that the continuum is partially seen in reflection as well. Unlike other symbiotic systems that show hard X-ray emission (CH Cyg, RT Cru, T CrB, GX1+4), SS73 17 is not known to have shown nova-like optical variability, X-ray flashes, or pulsations, and has always shown faint soft X-ray emission. As a result, although it is likely a white dwarf, the nature of the compact object in SS73 17 is still uncertain. SS73 17 is probably an extreme example of the recently discovered and relatively small class of hard X-ray emitting symbiotic systems.
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