A fast powerful X-ray transient from tidal disruption of a white dwarf

Abstract: Stars captured by black holes (BHs) can be tore apart by strong tidal force, producing electromagnetic flares. Some 100 tidal disruption events (TDEs) have been observed, involving invariably normal gaseous stars whose debris falls onto the BH fueling the flares over years. White dwarfs (WDs)-the most prevalent compact stars a million times denser and thus tougher than gaseous stars-can only be disrupted by intermediate-mass black holes (IMBHs) of 10^2-10^5 solar masses. WD-TDEs are predicted to generate more powerful and short-lived flares, but their evidence has been lacking. Here we report observations of a fast, luminous X-ray transient EP250702a. Its one-day-long peak showed strong recurrent flares extending to several tens of MeV in gamma-rays, indicating relativistic jet emission. The jet X-rays dropped sharply from exceeding 3 x 10^49 to around 10^44 erg/s within 20 days. These characteristics are inconsistent with any known transient phenomena other than a jetted-TDE evolving within a short timespan previously unseen-indicating the disruption of a white dwarf by an IMBH. At late times, a new soft component progressively dominates the X-ray spectrum, exhibiting extreme super-Eddington luminosity, possibly from an accretion disc. WD-TDEs open a new window to study elusive IMBHs and the otherwise invisible interior of degenerate stars.