A tidal disruption event from an intermediate-mass black hole revealed by comprehensive multi-wavelength observations

Tidal disruption events (TDEs) occur when a star crosses the tidal radius of a black hole (BH) and is ripped apart, providing a powerful way to probe dormant BHs over a wide mass range. In this study, we present our late-time observations and comprehensive multi-wavelength analyses of AT 2018cqh, a TDE at the center of a dwarf galaxy that exhibited successive flares in the optical, X-ray, and radio bands. We discovered an unexpected high-state X-ray plateau phase following the peak until the present time. Along with its reported prolonged rise lasting at least 550 days, these unique characteristics are consistent with the scenario of a TDE caused by an intermediate-mass black hole (IMBH) with a mass of approximately (1 − 6) × 105 solar masses. Furthermore, scaling relations derived from the host-galaxy properties indicated a similar BH mass in concert. This discovery highlights the invaluable role of TDEs in the search for elusive IMBHs. Black hole (BH) masses can be estimated from tidal disruption events (TDEs). Here, the authors show that AT 2018cqh, a TDE, exhibits unusual X-ray characteristics consistent with a TDE scenario involving an intermediate-mass BH.