Speaker
Description
Through its all-sky surveys, SRG/eROSITA has uncovered a large sample of X-ray transients associated with the nuclei of galaxies that show no signatures of prior AGN activity. A particular subclass is represented by tidal disruption events (TDEs), in which a flare of radiation is emitted as a star is ripped apart by wandering too close to a massive or supermassive black hole. Here, I will present the X-ray and multi-wavelength analysis of an exceptional candidate TDE found in the second eROSITA survey in a non-active galaxy at a redshift of z ∼ 0.1. The source showed properties characteristic of a TDE, such as 1) a soft X-ray spectrum (kT~100eV) 2) a flare-like evolution of the X-ray flux on timescales of months, 3) the appearance of broad (~2000 km/s) Balmer emission lines in follow-up optical spectra, undetected in archival observations, 4) the presence of HeII, Bowen and coronal lines, tracing a strong and fast ionizing continuum, 5) a bright WISE infrared flare, lagging behind the X-ray flare, likely arising from reprocessing of the primary radiation by a colder envelope. The late-time eROSITA data and Swift/XRT and XMM-Newton follow-up revealed intense short-term variability, indicating the presence of Quasi-Periodic Eruptions (QPEs) on timescales of ~16 hours. This source thus provides important insight into the connection of TDEs and QPEs, the latter being the potential electromagnetic counterparts of extreme mass ratio inspirals (EMRI).
