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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 atz= 0.054, with spectra showing [Fe x]λ6375 and [Fexiv]λ5303 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 Heiiλ4686 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 [Fexiv] weaken within 400 days of the optical peak, while [Fevii]λ5720, [Fevii]λ6087, and [Oiii]λλ4959,5007 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.
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This content will become publicly available on August 13, 2026
AT 2019aalc: A Bowen Fluorescence Flare with a Precursor Flare in an Active Galactic Nucleus
Abstract AT 2019aalc is a peculiar sequence of highly variable emission events observed towards the nucleus of the broad-line active galactic nucleus (AGN) SDSS J152416.66+045119.0. The system exhibited two distinct UV-optical flares (the first detected in 2019, the second one in 2023). Spectra obtained following the detection of the second flare revealed prominent Bowen fluorescence (BF) and high-ionization coronal emission lines, which were much weaker, if at all detectable, in a spectrum taken following the first flare. We present and analyze a large set of multi-wavelength, multi-epoch data for this source, with particular emphasis on optical spectroscopic monitoring conducted with the Las Cumbres Observatory network. During the relatively slow dimming that followed the second optical flare, the UV-optical light curve shows a sequence of minor rebrightening events, while the BF and the coronal lines vary (roughly) in tandem with these “bumps” in the broadband light curve. Most of the observed behavior of AT 2019aalc links it to the growing class of BF flares while setting it apart from canonical tidal disruption events. However, AT 2019aalc has some outstanding peculiarities, including two short flares seen in its soft X-ray light-curve during the dimming phase of the second optical flare, and which do not seem to be linked to the emission line variations. We discuss the optical and X-ray properties of the source and possible scenarios of the origin of the flare, in particular radiation pressure instabilities in the (preexisting) AGN accretion disk.
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- PAR ID:
- 10653566
- Publisher / Repository:
- AAS
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 989
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 173
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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