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arXiv · 2610.29137

NGC 3227 Blinks: An Extreme Changing-Look Event in a Seyfert Galaxy

Kaiwen Zhang·Michael S. Brotherton·Pu Du·Dong-Wei Bao·Bi-Xuan Zhao·Feng-na Fang·Yan-Rong Li·Chen Hu·Ming Xiao·Keith Horne·Gerard A. Kriss·Daniel Proga·Jian-Min Wang
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Abstract

We report a rapid optical changing-look event in the Seyfert galaxy NGC 3227: the optical continuum faded by more than 70% and broad H-beta emission nearly disappeared within weeks, before recovering within two months. Damped random walk simulations calibrated to the source's normal variability show that such a decline is unlikely for stochastic accretion fluctuations (p = 0.002). Simultaneous Swift monitoring reveals X-ray spectral hardening, pointing to enhanced line-of-sight absorption. During the dim state, reverberation mapping yields a persistent 6-8 day lag between the continuum and broad H-beta, showing that the broad-line region continued to reverberate and placing the obscurer interior to the broad-line region. Photoionization calculations require a fully ionized, Compton-thick column with N_H ~ 1.5 x 10^24 cm^-2 to reproduce the optical continuum suppression. Together, these observations demonstrate that compact, high-column-density obscurers interior to the broad-line region can produce extreme optical changing-look behavior on week timescales.

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Kaiwen Zhang, Michael S. Brotherton, Pu Du, Dong-Wei Bao, Bi-Xuan Zhao, Feng-na Fang, Yan-Rong Li, Chen Hu, Ming Xiao, Keith Horne, Gerard A. Kriss, Daniel Proga, Jian-Min Wang. 2026-10-21. NGC 3227 Blinks: An Extreme Changing-Look Event in a Seyfert Galaxy. https://arxiv.org/abs/2610.29137

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