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arXiv 0806.3876astro-ph
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NGC7213中铁K $α$系的BLR来源

A BLR origin for the iron K$α$ line in NGC7213

Stefano Bianchi, Fabio La Franca, Giorgio Matt, Matteo Guainazzi, Elena Jimenez Bailon, Anna Lia Longinotti, Fabrizio Nicastro, Laura Pentericci

摘要:

NGC 7213的X射线光谱没有康普顿反射的证据,这是明亮的塞弗特1中唯一的结果。因此,观测到的中性铁K $α$线不能与康普顿厚度的物质(如圆盘或环面)联系起来,而是由于康普顿厚度较薄的气体,宽线区(BLR)是最有可能的候选者。为了验证这一假设,在ESO NTT EMMI进行了长时间的钱德拉HETG观测以及准同步光学光谱观测。我们发现铁谱线的半高宽为$2 400^{+1 100}_{-600}$ km/s,与H $α$的宽谱分量$2640^{+110}_{-90}$ km/s的测量值完全一致。因此,NGC 7213是唯一一个铁K $α$线明确产生于BLR的塞弗特1星系。我们还确认了两条电离铁谱线的存在,并比以前更详细地研究了它们。共振线是Fe XXV三重态中的主要成分,因此表明起源于碰撞电离气体。如果是这样的话,这两条电离铁谱线的蓝移大约为1000 km/s,这可能是从X射线辐射中测量星暴风速度的第一个方法。

英文摘要:

The X-ray spectrum of NGC7213 is known to present no evidence for Compton reflection, a unique result among bright Seyfert 1s. The observed neutral iron K$α$ line, therefore, cannot be associated with a Compton-thick material, like the disc or the torus, but is due to Compton-thin gas, with the Broad Line Region (BLR) as the most likely candidate. To check this hypothesis, a long Chandra HETG observation, together with a quasi-simultaneous optical spectroscopic observation at the ESO NTT EMMI were performed. We found that the iron line is resolved with a FWHM=$2 400^{+1 100}_{-600}$ km/s, in perfect agreement with the value measured for the broad component of the H$α$, $2640^{+110}_{-90}$ km/s. Therefore, NGC7213 is the only Seyfert 1 galaxy whose iron K$α$ line is unambiguously produced in the BLR. We also confirmed the presence of two ionised iron lines and studied them in greater detail than before. The resonant line is the dominant component in the Fe XXV triplet, therefore suggesting an origin in collisionally ionised gas. If this is the case, the blueshift of around 1000 km/s of the two ionised iron lines could be the first measure of the velocity of a starburst wind from its X-ray emission.

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