PHL 1092是一个瞬变极弱X射线类星体
PHL 1092 as a transient extreme X-ray weak quasar
摘要：
我们报道了窄线类星体PHL 1092（z=0.396）的X射线历史中的一个剧烈变化事件。我们最新的2008年XMM-Newton观测显示，与大约4.5年前进行的上次观测相比，通量下降了~200，与历史通量相比下降了~135。尽管X射线的变化很大，紫外线通量仍然保持不变，使光学到X射线的斜率alpha_ox从-1.56到-2.44显著变陡，使PHL 1092成为最极端的X射线弱类星体之一。目前和以前的观测结果之间的软X射线光谱形状的相似性，以及持续的紫外线通量和光谱中没有任何显着的变化表明，吸收事件不太可能是观测到的变化的起源。如果排除吸收，PHL 1092的突然X射线减弱一定是由发射X射线的日冕的瞬时显著减弱或中断产生的。
英文摘要：
We report a dramatic variability event in the X-ray history of the Narrow-Line quasar PHL 1092 (z=0.396). Our latest 2008 XMM-Newton observation reveals a flux drop of ~200 with respect to the previous observation performed about 4.5 years earlier, and a drop of ~135 with respect to its historical flux. Despite the huge X-ray variation, the UV flux remains constant producing a very significant steepening of the optical to X-ray slope alpha_ox from -1.56 to -2.44, making PHL 1092 one of the most extreme X-ray weak quasars. The similarity in the soft X-ray spectral shape between the present and previous observations, together with the persistent UV flux and the lack of any dramatic change in the optical spectrum suggest that an absorption event is not likely to be the origin of the observed variation. If absorption is ruled out, the sudden X-ray weakness of PHL 1092 must be produced by a transient significant weakening or disruption of the X-ray emitting corona.
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