Mapping the Inner 0.1 pc of a Supermassive Black Hole Environment with the Tidal Disruption Event and Extreme Coronal-line Emitter AT 2022upj

Abstract

Extreme coronal-line emitters (ECLEs) are objects showing transient high-ionization lines in the centers of galaxies. They have been attributed to echoes of high-energy flares of ionizing radiation, such as those produced by tidal disruption events (TDEs), but have only recently been observed within hundreds of days after an optical transient was detected. AT 2022upj is a nuclear UV–optical flare at z = 0.054, with spectra showing [Fe x] λ 6375 and [Fe xiv ]​​​​​ λ 5303 during the optical peak, the earliest presence of extreme coronal lines during an ongoing transient. AT 2022upj is also the second ever ECLE (and the first with a concurrent flare) to show broad He ii λ 4686 emission, a key signature of optical/UV TDEs. We also detect X-ray emission during the optical transient phase, which may be related to the source of ionizing photons for the extreme coronal lines. Finally, we analyze the spectroscopic evolution of each emission line and find that [Fe x] and [Fe xiv ] weaken within 400 days of the optical peak, while [Fe vii ] λ 5720, [Fe vii ] λ 6087, and [O iii ] λλ 4959,5007 emerge over the same period. The velocities of the iron lines indicate circumnuclear gas within 0.1 pc of the central supermassive black hole (SMBH), while a dust echo inferred from NEOWISE data indicates that circumnuclear dust lies a minimum of 0.4 pc away, providing evidence of stratified material around an SMBH. AT 2022upj is thus the first confirmed ECLE–TDE with clear signatures of both classes and with spectroscopic evolution on a ∼year-long timescale. This event helps unveil the impacts of highly energetic flares such as TDEs on the complex environments around SMBHs.

Keywords

• Tidal disruption
• Galaxy accretion
• High energy astrophysics