硬激变变星的INTEGRAL/IBIS和Swift/XRT观测
INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variables
摘要：
第三次INTEGRAL/IBIS巡天的分析揭示了几个新的激变变星，其中大多数原来是中等极性的，从而证实这些物体是硬X射线的强发射体。在这里，我们提出了高能量谱的所有22个激变变量中检测到的第三IBIS调查，并提供了第一个平均频谱在20-100千电子伏波段为这一类。我们的分析表明，最适合的模型是一个热韧致辐射的平均温度<kT>为22 keV。最近，Swift/XRT（在0.3-10 keV能带内工作）跟踪了其中11个系统（10个中间极和1个极），从而使我们能够研究它们在~0.3-100 keV范围内的光谱行为。由于这种广泛的能量覆盖范围，这些源可以同时测量软组分和硬组分并估计它们的温度。软发射被认为起源于白矮星大气的受照射的两极，可以用黑体模型很好地描述，温度范围为~60-120 eV。硬发射，这应该是起源于光学薄的等离子体在后冲击波区域以上的磁极，确实是很好的模拟与韧致辐射模型的温度范围为16-33 keV，类似的值从积分数据单独获得。在几种情况下，我们还发现了复合吸收体的存在：一种完全覆盖源（NH ~（0.4-28）x 10^{21} cm^{-2}），另一种部分覆盖源（NH ~（0.7-9）x 10^{23} cm^{-2}）。只有在四种情况下（V709 Cas，GK Per，IGR J 06253 +7334和IGR J17303-0601），我们发现了6.4 keV处存在铁谱线的证据。我们讨论了我们的研究结果，根据系统参数和灾难性的变量/中间极性建模方案。
英文摘要：
The analysis of the third INTEGRAL/IBIS survey has revealed several new cataclysmic variables, most of which turned out to be intermediate polars, thus confirming that these objects are strong emitters in hard X-rays. Here we present high energy spectra of all 22 cataclysmic variables detected in the 3rd IBIS survey and provide the first average spectrum over the 20-100 keV band for this class. Our analysis indicates that the best-fit model is a thermal bremsstrahlung with an average temperature of <kT> ~22 keV. Recently, eleven (ten intermediate polars and one polar) of these systems have been followed-up by Swift/XRT (operating in the 0.3-10 keV energy band), thus allowing us to investigate their spectral behaviour over the range ~0.3-100 keV. Thanks to this wide energy coverage, it was possible for these sources to simultaneously measure the soft and hard components and estimate their temperatures. The soft emission, thought to originate in the irradiated poles of the white dwarf atmosphere, is well described by a blackbody model with temperatures in the range ~60-120 eV. The hard emission, which is supposed to be originated from optically thin plasma in the post-shock region above the magnetic poles, is indeed well modelled with a bremsstrahlung model with temperatures in the range ~16-33 keV, similar to the values obtained from the INTEGRAL data alone. In several cases we also find the presence of a complex absorber: one totally (with NH ~(0.4-28) x 10^{21} cm^{-2}) and one partially (with NH ~(0.7-9) x 10^{23} cm^{-2}) covering the source. Only in four cases (V709 Cas, GK Per, IGR J06253+7334 and IGR J17303-0601), we find evidence for the presence of an iron line at 6.4 keV. We discuss our findings in the light of the systems parameters and cataclysmic variables/intermediate polars modelling scenario.
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