Hyperluminous Supersoft X-Ray Sources in the Chandra Catalog

Abstract Hyperluminous supersoft X-ray sources (HSSs), such as bright extragalactic sources characterized by particularly soft X-ray spectra, offer a unique opportunity to study accretion onto supermassive black holes in extreme conditions. Examples of hyperluminous supersoft sources are tidal disruption events (TDEs), systems exhibiting quasiperiodic eruptions, changing-look active galactic nuclei, and anomalous nuclear transients. Although these objects are rare phenomena among the population of X-ray sources, we developed an efficient algorithm to identify promising candidates exploiting archival observations. In this work, we present the results of a search for HSSs in the recently released Chandra catalog of serendipitous X-ray sources. This archival search has been performed via both a manual implementation of the algorithm we developed and a novel machine learning–based approach. This search identified a new TDE, which might have occurred in an intermediate-mass black hole. This event occurred between 2001 and 2002, making it one of the first TDEs ever observed by Chandra.