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arXiv 2202.07007astro-ph.HE
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天鹅座A-2瞬变源的晚期X射线观测

Late-Time X-ray Observations of the Transient Source Cygnus A-2

Bradford Snios, Martijn De Vries, Paul E. J. Nulsen, Ralph P. Kraft, Aneta Siemiginowska, Michael W. Wise

摘要:

我们研究钱德拉观测强大的Fanaroff-Riley II类(FR II)射电星系天鹅座A的X射线对应的无线电瞬态天鹅座A-2,首次发现于2011年。观测是使用高分辨率照相机(HRC)仪器,以空间分辨天鹅座A-2和中央活动星系核(AGN)在0.42角秒的分离。生成发射区域的模拟图像,并且提取感兴趣区域的径向轮廓。模拟和观测结果之间的比较表明,在$1.04 \times 10^{-12}\rm\,erg\,cm^{-2}\,s^{-1}$的0.5-7.0 keV通量上限或$8.6\times 10^{42}\rm\,erg\,s^{-1}$的静止帧2-10 keV光度下,没有X射线探测到天鹅座A-2。我们估计天鹅座A-2的黑洞质量的基础上,我们的X射线通量限制,并发现它是一致的耀斑黑洞,而不是一个稳定的吸积源。HRC观测结果还与2016-2017年的ACIS档案数据进行了比较,AGN复合体的整体形态和通量极限在两个数据集之间一致。这种一致性是尽管堆积效应在ACIS这是以前被认为是偏见的活动星系核的观测形态。数据集之间的协议证明了利用天鹅座A的钱德拉档案数据以前所未有的精度分析其活动星系核的可行性。

英文摘要:

We examine Chandra observations of the powerful Fanaroff-Riley class II (FR II) radio galaxy Cygnus A for an X-ray counterpart to the radio transient Cygnus A-2 that was first detected in 2011. Observations are performed using the High-Resolution Camera (HRC) instrument in order to spatially resolve Cygnus A-2 and the central Active Galactic Nucleus (AGN) at a separation of 0.42 arcseconds. Simulated images are generated of the emission region, and radial profiles for the region of interest are extracted. A comparison between the simulations and observations reveals no X-ray detection of Cygnus A-2 to a 0.5-7.0 keV flux upper limit of $1.04 \times 10^{-12}\rm\,erg\,cm^{-2}\,s^{-1}$, or a rest-frame 2-10 keV luminosity of $8.6\times 10^{42}\rm\,erg\,s^{-1}$. We estimate the black hole mass of Cygnus A-2 based on our X-ray flux limit and find it to be consistent with a flaring black hole rather than a steadily accreting source. The HRC observations are additionally compared with archival ACIS data from 2016-2017, and both the overall morphology and the flux limits of the AGN complex agree between the two datasets. This consistency is despite the pile-up effect in ACIS which was previously considered to bias the observed morphology of the AGN. The agreement between the datasets demonstrates the viability of utilizing the archival Chandra data of Cygnus A to analyze its AGN at an unprecedented level of precision.

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