Exploring AGN behavior in real time: AT2021hdr and Ansky

Recent advancements in observational techniques have led to the discovery of extreme-variability events associated with active galactic nuclei (AGN). These rare phenomena offer an unprecedented opportunity to study AGN in real time. In this presentation, I will focus on two remarkable events detected using tools developed by the ALeRCE broker: AT2021hdr and Ansky. Thanks to ALeRCE’s rapid processing of large data volumes and timely alerts, these objects were identified in their early stages, enabling prompt multiwavelength follow-up observations. AT2021hdr displays oscillations with timescales of ~90 days in its light curves across X-ray, UV, and optical bands, and its unusual behavior may be linked to the tidal disruption of a gas cloud by a binary supermassive black hole (SMBH). Ansky, on the other hand, exhibits some of the most extreme quasi-periodic eruptions (QPEs) observed to date, with burst durations of 1.5 days, a 4.5-day peak-to-peak recurrence time, and an average integrated energy output about 10 times higher than other QPEs. Ansky appears to be entering an active phase, challenging current theoretical models. These findings provide valuable insights into the dynamic environments around SMBHs, including tidal disruption events, episodic mass transfer, and the potential existence of SMBH binaries.