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arXiv 1105.0893astro-ph.HE
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XMM对三个快速BAT选择的活动星系核的跟踪观测

XMM Follow-Up Observations of Three Swift BAT-Selected Active Galactic Nuclei

M. L. Trippe, C. S. Reynolds, M. Koss, R. F. Mushotzky, L. M. Winter

摘要:

我们目前的XMM-牛顿观测的三个AGN作为狩猎的一部分,找到非常模糊的康普顿厚AGN。对于大于10^25 cm^-2的暗柱,活动星系核只有在能量低于10 keV时才能通过反射/散射辐射被观测到,其特征是具有平坦的幂律。因此,我们选择了三个对象(ESO 417-G 006,IRAS 05218-1212和MCG-01 - 05 -047)从斯威夫特BAT硬X射线调查目录与斯威夫特X射线望远镜XRT 0.5-10 keV光谱与平坦的幂律指数作为候选康普顿厚源的后续观测与更敏感的仪器XMM-牛顿。然而,XMM光谱,排除反射为主的模型的基础上观察到的Fe K-α线的弱点。相反,光谱是很好的拟合的幂律连续被康普顿薄吸收体掩盖的模型,加上软过剩。这一结果与之前对另外两个BAT探测到的活动星系核的后续观测结果一致。因此,在22个月的BAT目录中,有6个活动星系核具有明显平坦的斯威夫特XRT光谱,所有5个有后续观测的活动星系核都不太可能是康普顿厚度的。我们还介绍了其中两个天体的新光谱,IRAS 05218-1212和MCG-01 - 05 -047。有趣的是,虽然这两个活动星系核有相似的X射线光谱,但它们的光谱却完全不同,这增加了反对活动星系核几何统一模型最简单形式的证据。IRAS 05218-1212在光学上看起来像是塞弗特1,尽管它的X射线光谱显示了约8.5x10^22 cm^-2的视线吸收柱。MCG-01 - 05 -047的光谱没有显示活动星系核活动的迹象;它看起来像一个正常的星系。

英文摘要:

We present XMM-Newton observations of three AGN taken as part of a hunt to find very heavily obscured Compton-thick AGN. For obscuring columns greater than 10^25 cm^-2, AGN are only visible at energies below 10 keV via reflected/scattered radiation, characterized by a flat power-law. We therefore selected three objects (ESO 417-G006, IRAS 05218-1212, and MCG -01-05-047) from the Swift BAT hard X-ray survey catalog with Swift X-ray Telescope XRT 0.5-10 keV spectra with flat power-law indices as candidate Compton-thick sources for follow-up observations with the more sensitive instruments on XMM-Newton. The XMM spectra, however, rule out reflection-dominated models based on the weakness of the observed Fe K-alpha lines. Instead, the spectra are well-fit by a model of a power-law continuum obscured by a Compton-thin absorber, plus a soft excess. This result is consistent with previous follow-up observations of two other flat-spectrum BAT-detected AGN. Thus, out of the six AGN in the 22-month BAT catalog with apparently flat Swift XRT spectra, all five that have had follow-up observations are not likely Compton-thick. We also present new optical spectra of two of these objects, IRAS 05218-1212 and MCG -01-05-047. Interestingly, though both these AGN have similar X-ray spectra, their optical spectra are completely different, adding evidence against the simplest form of the geometric unified model of AGN. IRAS 05218-1212 appears in the optical as a Seyfert 1, despite the ~8.5x10^22 cm^-2 line-of-sight absorbing column indicated by its X-ray spectrum. MCG -01-05-047's optical spectrum shows no sign of AGN activity; it appears as a normal galaxy.

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