Improving the selection of changing-look AGNs through multiwavelength photometric variability
Improving the selection of changing-look AGNs through multiwavelength photometric variability
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DOI：
10.1093/mnras/stad1893
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发表时间：
2023-06
影响因子：
4.8
通讯作者：
E. L'opez-Navas;P. S'anchez-S'aez;P. Ar'evalo;S. Bernal;M. Graham;L. Hernandez-Garcia;D. Homan;M. Krumpe;G. Lamer;P. Lira;M. L. Mart'inez-Aldama;A. Merloni;S. R'ios;M. Salvato;D. Stern;D. Tub'in-Arenas
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文献类型：
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作者：
E. L'opez-Navas;P. S'anchez-S'aez;P. Ar'evalo;S. Bernal;M. Graham;L. Hernandez-Garcia;D. Homan;M. Krumpe;G. Lamer;P. Lira;M. L. Mart'inez-Aldama;A. Merloni;S. R'ios;M. Salvato;D. Stern;D. Tub'in-Arenas
我们给出了通过在光谱上被归类为类型2的活动星系核(AGN)样本中搜索类型1光学可变性而发现的30个变化外观(CL)候选者的第二纪元光谱。我们使用基于随机森林的光曲线分类器和光谱跟踪，确认50%的候选者为开启的变化外观(CL)。为了改进这种选择方法，并更好地了解未确认的候选CL的性质，我们进行了包括光学、中红外(MIR)和X射线数据的多波长变异性分析，并比较了本工作中确认的和未确认的CL的结果。我们发现，大多数未确认的CLS与以宿主星系贡献为主的弱I型一致，表现出较弱的光学和MIR变率。相反，被确认的CLS呈现出更强的光学涨落，并且随着时间的推移，它们的MIR通量和颜色W1-W2经历了很长时间(从5年到10年)的增加。在0.2-2.3keV波段，与档案上限相比，具有SRG/eROSITA探测的11个CLS中至少有4个的通量增加。这些共同的特征使我们能够从候选列表中选择最有前景的CL，从而产生9个具有与我们的CL样本相似的多波长光度学特性的光源。在未来的大规模调查中，使用光学和MIR光曲线的机器学习算法将非常有用地识别CLS。
We present second epoch optical spectra for 30 changing-look (CL) candidates found by searching for Type-1 optical variability in a sample of active galactic nuclei (AGNs) spectroscopically classified as Type 2. We use a random-forest-based light-curve classifier and spectroscopic follow-up, confirming 50 per cent of candidates as turning-on CLs. In order to improve this selection method and to better understand the nature of the not-confirmed CL candidates, we perform a multiwavelength variability analysis including optical, mid-infrared (MIR), and X-ray data, and compare the results from the confirmed and not-confirmed CLs identified in this work. We find that most of the not-confirmed CLs are consistent with weak Type 1s dominated by host-galaxy contributions, showing weaker optical and MIR variability. On the contrary, the confirmed CLs present stronger optical fluctuations and experience a long (from five to ten years) increase in their MIR fluxes and the colour W1–W2 over time. In the 0.2–2.3 keV band, at least four out of 11 CLs with available SRG/eROSITA detections have increased their flux in comparison with archival upper limits. These common features allow us to select the most promising CLs from our list of candidates, leading to nine sources with similar multiwavelength photometric properties to our CL sample. The use of machine learning algorithms with optical and MIR light curves will be very useful to identify CLs in future large-scale surveys.