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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. 

Abstract Transient accretion events onto supermassive black holes (SMBHs), such as tidal disruption events (TDEs), Bowen Fluorescence Flares (BFFs), and active galactic nuclei (AGNs), which are accompanied by sudden increases of activity, offer a new window onto the SMBH population, accretion physics, and stellar dynamics in galaxy centers. However, such transients are rare and finding them in wide-field transient surveys is challenging. Here we present the results of a systematic real-time search for SMBH-related transients in Zwicky Transient Facility (ZTF) public alerts, using various search queries. We examined 345 rising events coincident with a galaxy nucleus, with no history of previous activity, of which 223 were spectroscopically classified. Of those, five (2.2%) were TDEs, one (0.5%) was a BFF, and two (0.9%) were AGN flares. Limiting the search to blue events, the fraction of TDEs nearly doubles to 4.1%, and no TDEs are missed. Limiting the search further to candidate post-starburst galaxies increases the relative number of TDEs to 16.7%, but the absolute numbers in such a search are small. The main contamination source is supernovae (95.1% of classified events), of which the majority (82.2% of supernovae) are of Type Ia. In a comparison set of 39 events with limited photometric history, the AGN contamination increases to ∼30%. Host galaxy offset is not a significant discriminant of TDEs in current ZTF data, but might be useful in higher-resolution data. Our results can be used to quantify the efficiency of various SMBH-related transient search strategies in optical surveys such as ZTF and the Legacy Survey of Space and Time. 

Abstract Flares produced following the tidal disruption of stars by supermassive black holes can reveal the properties of the otherwise dormant majority of black holes and the physics of accretion. In the past decade, a class of optical-ultraviolet tidal disruption flares has been discovered whose emission properties do not match theoretical predictions. This has led to extensive efforts to model the dynamics and emission mechanisms of optical-ultraviolet tidal disruptions in order to establish them as probes of supermassive black holes. Here we present the optical-ultraviolet tidal disruption event AT 2022dbl, which showed a nearly identical repetition 700 days after the first flare. Ruling out gravitational lensing and two chance unrelated disruptions, we conclude that at least the first flare represents the partial disruption of a star, possibly captured through the Hills mechanism. Since both flares are typical of the optical-ultraviolet class of tidal disruptions in terms of their radiated energy, temperature, luminosity, and spectral features, it follows that either the entire class are partial rather than full stellar disruptions, contrary to the prevalent assumption, or some members of the class are partial disruptions, having nearly the same observational characteristics as full disruptions. Whichever option is true, these findings could require revised models for the emission mechanisms of optical-ultraviolet tidal disruption flares and a reassessment of their expected rates. 

Abstract AT 2020mot is a typical UV/optical tidal disruption event (TDE) with no radio or X-ray signatures in a quiescent host. We find ani-band excess and rebrightening along the decline of the light curve which could be due to two consecutive dust echoes from the TDE. We model our observations following van Velzen et al. and find that the near-infrared light curve can be explained by concentric rings of thin dust within ∼0.1 pc of a ∼6 × 10⁶M_⊙supermassive black hole (SMBH), among the smallest scales at which dust has been inferred near SMBHs. We find dust covering factors of orderf_c≤ 2%, much lower than found for dusty tori of active galactic nuclei. These results highlight the potential of TDEs for uncovering the environments around black holes when including near-infrared observations in high-cadence transient studies.