The BAT AGN Spectroscopic Survey. XVIII. Searching for Supermassive Black Hole Binaries in X-Rays
The BAT AGN Spectroscopic Survey. XVIII. Searching for Supermassive Black Hole Binaries in X-Rays
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DOI：
10.3847/1538-4357/ab952d
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发表时间：
2019-12
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通讯作者：
Tingting Liu;M. Koss;L. Blecha;C. Ricci;B. Trakhtenbrot;R. Mushotzky;F. Harrison;K. Ichikawa;D. Kakkad;K. Oh;M. Powell;G. Privon;K. Schawinski;T. Taro Shimizu;Krista Smith;D. Stern;E. Treister;C. Urry
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作者：
Tingting Liu;M. Koss;L. Blecha;C. Ricci;B. Trakhtenbrot;R. Mushotzky;F. Harrison;K. Ichikawa;D. Kakkad;K. Oh;M. Powell;G. Privon;K. Schawinski;T. Taro Shimizu;Krista Smith;D. Stern;E. Treister;C. Urry
理论预测，超大质量黑洞双星（SMBHB）可以被观测到作为一个发光的活动星系核（AGN），其轨道时间尺度的顺序周期性变化。在X射线中，周期性变化可能是由包括相对论多普勒增强和冲击在内的机制引起的。在这里，我们提出了第一个系统的搜索周期性活动星系核使用941硬X射线光变曲线（14-195千电子伏）从第一个105个月的斯威夫特爆发警报望远镜（BAT）调查（2004-2013）。我们没有在Swift-BAT中找到周期性活动星系核的证据，包括之前报道的SMBHB候选者MCG+11−11−032。我们发现，零检测是一致的组合的上限二进制人口在活动星系核在我们所采用的模型，其预期的周期性变化幅度，和BAT调查的特点。我们还研究了SMBHB对正常活动星系核X射线变化的可探测性的背景下，扩展的伦琴调查与成像望远镜阵列（eROSITA）调查。在我们的假设下，一个二进制人口和周期信号，他们产生的，这有数百天的长周期，高达13%的真正的周期双星可以鲁棒地区别于正常的变量活动星系核与理想的均匀采样。然而，我们表明，现实eROSITA采样可能是不敏感的长周期的二进制文件，因为较长的观测间隙降低其可检测性。相比之下，大的观测差距并没有减少探测短，几天周期的双星的前景，因为19%可以成功地恢复，其中绝大多数可以通过调查的前半部分确定。
Theory predicts that a supermassive black hole binary (SMBHB) could be observed as a luminous active galactic nucleus (AGN) that periodically varies on the order of its orbital timescale. In X-rays, periodic variations could be caused by mechanisms including relativistic Doppler boosting and shocks. Here we present the first systematic search for periodic AGNs using 941 hard X-ray light curves (14–195 keV) from the first 105 months of the Swift Burst Alert Telescope (BAT) survey (2004–2013). We do not find evidence for periodic AGNs in Swift-BAT, including the previously reported SMBHB candidate MCG+11−11−032. We find that the null detection is consistent with the combination of the upper-limit binary population in AGNs in our adopted model, their expected periodic variability amplitudes, and the BAT survey characteristics. We have also investigated the detectability of SMBHBs against normal AGN X-ray variability in the context of the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) survey. Under our assumptions of a binary population and the periodic signals they produce, which have long periods of hundreds of days, up to 13% true periodic binaries can be robustly distinguished from normal variable AGNs with the ideal uniform sampling. However, we demonstrate that realistic eROSITA sampling is likely to be insensitive to long-period binaries because longer observing gaps reduce their detectability. In contrast, large observing gaps do not diminish the prospect of detecting binaries of short, few-day periods, as 19% can be successfully recovered, the vast majority of which can be identified by the first half of the survey.