Extreme variability in an active galactic nucleus: Gaia16aax
Extreme variability in an active galactic nucleus: Gaia16aax
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DOI：
10.1093/mnras/staa186
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发表时间：
2020-01
影响因子：
4.8
通讯作者：
G. Cannizzaro;M. Fraser;P. Jonker;J. Pringle;S. Mattila;P. Hewett;T. Wevers;E. Kankare;Z. Kostrzewa
中科院分区：
文献类型：
--
作者：
G. Cannizzaro;M. Fraser;P. Jonker;J. Pringle;S. Mattila;P. Hewett;T. Wevers;E. Kankare;Z. Kostrzewa
我们提出了发光核瞬态Gaia 16 aax的多波长后续活动的结果，该活动于2016年1月首次发现。瞬态在空间上与z = 0.25的活动星系核一致，拥有质量为${\sim } 6\times 10^8\，\mathrm{M}_\odot$的黑洞。在不到1年的时间尺度内，核心在盖亚G波段增亮超过1等，然后在接下来的3年内逐渐恢复到爆发前的状态。源的光谱显示出与爆发前光谱中存在的类似的宽巴耳末线。在爆发过程中，H α和H β发射线出现一个次峰。我们还报告发现两个瞬态具有相似的光变曲线的演变和光谱：Gaia 16 aka和Gaia 16 ajq。我们认为可能的情况来解释所观察到的爆发。我们排除了由微透镜事件、可变尘埃吸收或中子星星与吸积盘中恒星质量黑洞之间的潮汐相遇引起的瞬态事件。我们认为在吸积流的盘的内部的变化，或一个星星1 \，\mathrm{M}_{\odot }$由一个快速旋转的超大质量黑洞的潮汐破坏事件作为最合理的方案。我们注意到，三个盖亚瞬变的光变曲线之间的相似性可能是盖亚警报选择标准的函数。
We present the results of a multiwavelength follow-up campaign for the luminous nuclear transient Gaia16aax, which was first identified in 2016 January. The transient is spatially consistent with the nucleus of an active galaxy at z = 0.25, hosting a black hole of mass ${\sim }6\times 10^8\, \mathrm{M}_\odot$. The nucleus brightened by more than 1 mag in the Gaia G band over a time-scale of less than 1 yr, before fading back to its pre-outburst state over the following 3 yr. The optical spectra of the source show broad Balmer lines similar to the ones present in a pre-outburst spectrum. During the outburst, the H α and H β emission lines develop a secondary peak. We also report on the discovery of two transients with similar light-curve evolution and spectra: Gaia16aka and Gaia16ajq. We consider possible scenarios to explain the observed outbursts. We exclude that the transient event could be caused by a microlensing event, variable dust absorption or a tidal encounter between a neutron star and a stellar mass black hole in the accretion disc. We consider variability in the accretion flow in the inner part of the disc, or a tidal disruption event of a star ${\ge } 1 \, \mathrm{M}_{\odot }$ by a rapidly spinning supermassive black hole as the most plausible scenarios. We note that the similarity between the light curves of the three Gaia transients may be a function of the Gaia alerts selection criteria.