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arXiv 1505.01166astro-ph.GAastro-ph.HE
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Seyfert 2星系的X射线光谱变率

X-ray spectral variability of Seyfert 2 galaxies

L. Hernández-García, J. Masegosa, O. González-Martín, I. Márquez

摘要:

活动星系核在电磁波谱上的变化性有助于限制这些星系的物理性质。这是一系列论文的第三篇,目的是研究活动星系核不同家族的X射线可变性。本文的主要目的是研究光选2型塞弗特星系的光变模式。我们使用Veron-Cetty和Veron目录中的26个Seyferts,并使用Chandra和/或XMM-Newton公共档案中不同时期的数据,时间尺度从几小时到几年不等。同时对同一源的所有光谱进行拟合,并在模型中引入不同的参数。只要有可能,就研究短期变化和/或长期紫外线通量变化。我们将样品分为康普顿厚、康普顿薄和变化外观的候选者。在25个被分析的源中,有11个显示出长期的变化; 8个(11个中的8个)是康普顿薄的,1个(12个中的1个)是康普顿厚的,还有两个变化的候选者也是可变的。X射线变化的主要驱动因素与核功率有关(9例),而软能量的变化或与硬X射线吸收剂有关的变化则不太常见,在许多情况下,这些变化伴随着核连续谱的变化。我们首次报道了两个变星MARK 273和NGC 7319。远离原子核的恒定反射分量加上可变的原子核连续谱能够解释我们的大部分结果;康普顿厚的候选者被反射所支配,这抑制了它们的连续谱,使它们看起来更暗,没有显示出变化,而康普顿薄和变化的候选者显示出变化。

英文摘要:

Variability across the electromagnetic spectrum is a property of AGN that can help constraining the physical properties of these galaxies. This is the third of a serie of papers with the aim of studying the X-ray variability of different families of AGN. The main purpose of this work is to investigate the variability pattern in a sample of optically selected type 2 Seyfert galaxies. We use the 26 Seyferts in the Veron-Cetty and Veron catalogue with data available from Chandra and/or XMM-Newton public archives at different epochs, with timescales ranging from a few hours to years. All the spectra of the same source are simultaneously fitted and we let different parameters to vary in the model. Whenever possible, short-term variations and/or long-term UV flux variations are studied. We divide the sample in Compton-thick, Compton-thin, and changing-look candidates. Short-term variability at X-rays is not found. From the 25 analyzed sources, 11 show long-term variations; eight (out of 11) are Compton-thin, one (out of 12) is Compton-thick, and the two changing-look candidates are also variable. The main driver for the X-ray changes is related to the nuclear power (nine cases), while variations at soft energies or related with absorbers at hard X-rays are less common, and in many cases these variations are accompained with variations of the nuclear continuum. At UV frequencies nuclear variations are nor found. We report for the first time two changing-look candidates, MARK273 and NGC7319. A constant reflection component located far away from the nucleus plus a variable nuclear continuum are able to explain most of our results; the Compton-thick candidates are dominated by reflection, which supresses their continuum making them seem fainter, and not showing variations, while the Compton-thin and changing-look candidates show variations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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