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

Wang, Jialai; Huang, Mengqiu; Xue, Yongquan; Jiang, Ning; Huang, Shifeng; Wang, Yibo; Zhu, Jiazheng; Zhu, Shifu et al. · Nat Commun · 2026

basic_science · Level V

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Abstract

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) × 10<sup>5</sup> 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.