AT2019aalc Identified as a Candidate for Repeating Tidal Disruption Events in Active Galactic Nuclei

Recent observations have classified the astronomical transient AT2019aalc as a candidate for a repeating tidal disruption event (TDE) in an active galactic nucleus (AGN). This classification follows a multi-wavelength monitoring program conducted in 2023, which revealed significant re-brightening of the source four years after its initial discovery. The findings indicate that AT2019aalc, located in a Seyfert-1 galaxy, exhibited a uniquely bright ultraviolet counterpart and multiple X-ray flares during its second optical flaring episode. Notably, this second flare was accompanied by infrared dust echo emissions, similar to the first flare observed.

The study, led by Patrik Milán Veres and co-authored by 17 researchers, also identified a long-term radio flare with an inverted spectrum. Optical spectroscopic observations showed the presence of Bowen fluorescence lines and strong high-ionization coronal lines, suggesting an extreme level of ionization within the system. These characteristics led to the classification of AT2019aalc as a Bowen Fluorescence Flare (BFF), a relatively new subclass of flaring AGNs. Furthermore, the study found that another BFF, AT2021loi, is spatially coincident with a high-energy neutrino event, hinting at a potential connection between extreme coronal line emitters, BFFs, and TDEs in AGNs.

The implications of these findings are significant for understanding the behavior of massive black holes and their interactions with surrounding stars. The research provides new insights into the mechanisms behind TDEs and their potential links to high-energy astrophysical phenomena. The full paper can be accessed at arXiv:2408.17419.