科研之友
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摘要
We present the first X-ray observations of three sources belonging to a new AGN class: the naked AGNs. Based on optical spectroscopic studies, these sources appear as classical type 2 ( obscured) AGNs, with only narrow emission lines. However, long-term optical monitoring campaigns, carried out over more than two decades, show that the same sources are strongly variable, like type 1 ( unobscured) AGNs. Based on short Chandra observations, the sources appear to be fairly bright in the X-rays, with typical Seyfert 1 values for the photon index ( Gamma similar to 1.8) and without significant intrinsic absorption, supporting the conclusion that some bright AGNs may genuinely lack a broad-line region. Future broadband studies as well as deeper X-ray observations, probing both the spectral and the temporal properties of the naked AGNs, are crucial to shed light on the central engine of these sources, which may be representative of a large class of AGNs.
- 出版日期2007-6-20
