标题： 真正II型塞弗特星系的同时X射线和光学观测 显示英文标题

标题： Simultaneous X-ray and optical observations of true Type 2 Seyfert galaxies

摘要： 我们展示了对“真正的”Ⅱ型 Seyfert 星系候选体进行的联合 X 射线和光学观测活动的结果，即没有宽线区（BLR）的活动星系核（AGN）。从最初的由 8 个源组成的样本中，发现一个天体 IC1631 是一个被错误分类的恒星形成星系，另一个 Q2130-431 显示出宽光学谱线，而另外两个 IRAS01428-0404 和 NGC4698 很可能被视线方向上的康普顿厚气体吸收。因此，这四个源并非如文献所述那样是未被吸收的 Seyfert 2 型星系。另一方面，我们确认 NGC3147、NGC3660 和 Q2131-427 属于真正的Ⅱ型 Seyfert 星系，因为它们的光学谱线没有任何宽成分的证据，且 X 射线能谱中也无遮挡现象。这三个源具有较低的吸积率（$\dot{m}= L_{bol}/L_{Edd} \la0.01$），与理论模型一致，该模型预测当吸积率低于临界值（$L_{bol}/L_{Edd}$）时，BLR 将消失。最后一个源 Mrk273x 即使在这些与吸积相关的统一模型版本中也代表了一个例外，由于其高 X 射线亮度和吸积率，且没有遮挡的证据。然而，它作为 Seyfert 2 型星系的光学分类仅基于 H\beta 的宽成分缺失，这是由于缺乏覆盖 H\alpha 波段的光学光谱。 显示英文摘要

摘要： We present the results of a campaign of simultaneous X-ray and optical observations of `true' Type 2 Seyfert galaxies candidates, i.e. AGN without a Broad Line Region (BLR). Out of the initial sample composed by 8 sources, one object, IC1631, was found to be a misclassified starburst galaxy, another, Q2130-431, does show broad optical lines, while other two, IRAS01428-0404 and NGC4698, are very likely absorbed by Compton-thick gas along the line of sight. Therefore, these four sources are not unabsorbed Seyfert 2s as previously suggested in the literature. On the other hand, we confirm that NGC3147, NGC3660, and Q2131-427 belong to the class of true Type 2 Seyfert galaxies, since they do not show any evidence for a broad component of the optical lines nor for obscuration in their X-ray spectra. These three sources have low accretion rates ($\dot{m}= L_{bol}/L_{Edd} \la0.01$), in agreement with theoretical models which predict that the BLR disappears below a critical value of $L_{bol}/L_{Edd}$. The last source, Mrk273x, would represent an exception even of this accretion-dependent versions of the Unification Models, due to its high X-ray luminosity and accretion rate, and no evidence for obscuration. However, its optical classification as a Seyfert 2 is only based on the absence of a broad component of the H\beta, due to the lack of optical spectra encompassing the H\alpha\ band.