Anatomy of the AGN in NGC 5548 IV. The short-term variability of the outflows
Anatomy of the AGN in NGC 5548 IV. The short-term variability of the outflows
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NGC 5548 IV 中活动星系核的解剖。
DOI：
10.1051/0004-6361/201525934
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发表时间：
2015
影响因子：
6.5
通讯作者：
M. Whewell
中科院分区：
文献类型：
--
作者：
L. D. Gesu;E. Costantini;J. Ebrero;M. Mehdipour;J. Kaastra;J. Kaastra;F. Ursini;P. Petrucci;M. Cappi;G. Kriss;G. Kriss;S. Bianchi;G. Branduardi‐Raymont;B. Marco;A. Rosa;S. Kaspi;S. Paltani;Ciro Pinto;G. Ponti;K. Steenbrugge;M. Whewell
在一个广泛的多波长活动，我们在2013 - 2014年进行，我们发现了原型塞弗特1星系NGC 5548在一个不寻常的条件下，沉重和持久的遮蔽。新发现的“遮光剂”吸收了我们视线上沿着的大部分软X射线连续谱，并降低了经典暖吸收体接收到的电离光度。我们对整个活动期间使用XMM-Newton和Chandra收集的高分辨率X射线光谱进行了分析，这些光谱适合研究模糊吸收体和经典热吸收体的变化性。这些X射线观测之间的时间间隔从两天到八个月不等。在这些时间尺度上，遮蔽器在列密度和覆盖分数上都是可变的。这与斑片状风的图像是一致的。最显著的变化发生在2013年9月，当时光源亮了两周。一个更高和更陡的内在连续和更低的模糊覆盖分数都需要解释的光谱形状在耀斑。我们认为，软X射线源背后的遮蔽的几何变化导致所观察到的下降的覆盖分数。由于较高的软X射线连续谱水平，2013年9月的钱德拉光谱是该活动中唯一可以检测到暖吸收体的个别特征的X射线光谱。光谱显示来自Fe-UTA、Oiv和Ov的吸收，与属于历史上NGC 5548暖吸收体的低电离对应物一致。因此，我们确认，温暖的吸收体已响应于由遮光剂引起的电离光度下降。
During an extensive multiwavelength campaign that we performed in 2013 2014, we found the prototypical Seyfert 1 galaxy NGC 5548 in an unusual condition of heavy and persistent obscuration. The newly discovered “obscurer” absorbs most of the soft X-ray continuum along our line of sight and lowers the ionizing luminosity received by the classical warm absorber. We present the analysis of the high resolution X-ray spectra collected with XMM-Newton and Chandra throughout the campaign, which are suitable to investigate the variability of both the obscurer and classical warm absorber. The time separation between these X-ray observations range from two days to eight months. On these timescales the obscurer is variable both in column density and in covering fraction. This is consistent with the picture of a patchy wind. The most significant variation occurred in September 2013 when the source brightened for two weeks. A higher and steeper intrinsic continuum and a lower obscurer covering fraction are both required to explain the spectral shape during the flare. We suggest that a geometrical change of the soft X-ray source behind the obscurer causes the observed drop in the covering fraction. Because of the higher soft X-ray continuum level, the September 2013 Chandra spectrum is the only X ray spectrum of the campaign in which individual features of the warm absorber could be detected. The spectrum shows absorption from Fe-UTA, Oiv, and Ov, consistent with belonging to the lower-ionization counterpart of the historical NGC 5548 warm absorber. Hence, we confirm that the warm absorber has responded to the drop in the ionizing luminosity caused by the obscurer.