标题： 来自PTF的短周期变星类星体种群作为超大质量黑洞双星候选者 显示英文标题

标题： A Population of Short-Period Variable Quasars from PTF as Supermassive Black Hole Binary Candidates

摘要： 超大质量黑洞双星（SMBHBs）在亚天文单位的距离上在星系核中应该是常见的，这是由于频繁的星系合并。围绕双星的盘状结构的流体动力学模拟预测了质量吸积率在与双星轨道周期相当的时间尺度上的强烈周期性调制。因此，SMBHBs可能通过其亮度的周期性调制被识别出来。我们在帕洛马瞬变工厂（PTF）的光度数据库中35,383个光谱确认的类星体样本中进行了一项统计搜索，寻找周期性变化。我们分析了Lomb-Scargle周期图，并通过将每个单独类星体的变化建模为阻尼随机游走（DRW）来评估发现的重要性。我们识别出50个超出DRW模型显著周期性的类星体，通常具有几百天的短周期。我们发现其中33个在包括来自中间PTF和卡特里娜实时瞬变调查（CRTS）的额外光学数据重新分析其周期图后仍然显著。假设观测到的周期对应于红移后的SMBHB轨道周期，我们得出结论，我们的发现与一个质量不相等的SMBHB群体一致，典型的质量比低至q = M2/M1 ~ 0.01。 显示英文摘要

摘要： Supermassive black hole binaries (SMBHBs) at sub-parsec separations should be common in galactic nuclei, as a result of frequent galaxy mergers. Hydrodynamical simulations of circumbinary discs predict strong periodic modulation of the mass accretion rate on time-scales comparable to the orbital period of the binary. As a result, SMBHBs may be recognized by the periodic modulation of their brightness. We conducted a statistical search for periodic variability in a sample of 35,383 spectroscopically confirmed quasars in the photometric database of the Palomar Transient Factory (PTF). We analysed Lomb-Scargle periodograms and assessed the significance of our findings by modeling each individual quasar's variability as a damped random walk (DRW). We identified 50 quasars with significant periodicity beyond the DRW model, typically with short periods of a few hundred days. We find 33 of these to remain significant after a re-analysis of their periodograms including additional optical data from the intermediate-PTF and the Catalina Real-Time Transient Survey (CRTS). Assuming that the observed periods correspond to the redshifted orbital periods of SMBHBs, we conclude that our findings are consistent with a population of unequal-mass SMBHBs, with a typical mass ratio as low as q = M2/M1 ~ 0.01.