An Unusual Mid-infrared Flare in a Type 2 AGN: An Obscured Turning-on AGN or Tidal Disruption Event?

Year: 2019

Type: article

Abstract: We report the discovery of an exceptional MIR flare in a Type 2 AGN, SDSS J165726.81+234528.1, at z = 0.059. This object brightened by 3 mag in the Wide-field Infrared Survey Explorer (WISE) W1 and W2 bands between 2015 and 2017 (and has been fading since 2018), without significant changes (≲0.2 mag) in the optical over the same period of time. Based on the WISE light curves and near-IR imaging, the flare is more significant at longer wavelengths, suggesting an origin of hot dust emission. The estimated black hole mass (∼106.5 M ⊙) from different methods places its peak bolometric luminosity around the Eddington limit. The high luminosity of the MIR flare and its multiyear timescale suggest that it most likely originated from reprocessed dust radiation in an extended torus surrounding the AGN, instead of from stellar explosions. The MIR color variability is consistent with known changing-look AGN and tidal disruption events (TDEs), but inconsistent with normal supernovae. We suggest that it is a turning-on Type 2 AGN or TDE, where the optical variability is obscured by the dust torus during the transition. This MIR flare event reveals a population of dramatic nuclear transients that are missed in the optical.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/ab481a

Authors: Qian Yang, Yue Shen, Xin Liu, Xue-Bing Wu, Linhua Jiang, Jinyi Shangguan, Matthew J. Graham, Su Yao

Institutions: University of Illinois Urbana-Champaign, National Center for Supercomputing Applications, Peking University, Max Planck Institute for Extraterrestrial Physics, California Institute of Technology

Language: English

Topic: Galaxies: Formation, Evolution, Phenomena

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: bronze

Funders: National Science Foundation, Smithsonian Institution, U.S. Department of Energy, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Gordon and Betty Moore Foundation, Princeton University, Ohio State University, California Institute of Technology, University of Washington, Johns Hopkins University, University of Pittsburgh, Case Western Reserve University, Drexel University, Universität Basel, University of Portsmouth, New Mexico State University, Space Telescope Science Institute, Queen's University Belfast, Durham University, National Natural Science Foundation of China, Chinese Academy of Sciences, Queen's University, Max-Planck-Gesellschaft, National Central University, Stockholms Universitet, Eötvös Loránd Tudományegyetem, Max-Planck-Institut für Astronomie, Jet Propulsion Laboratory, University of California, Los Angeles, Smithsonian Astrophysical Observatory, Science Mission Directorate, Deutsches Elektronen-Synchrotron, U.S. Naval Observatory, Planetary Science Division, Fermilab, Los Alamos National Laboratory

OpenAlex ID: W2982723294