HXMT identification of a non-thermal X-ray burst from SGR J1935+2154 and with FRB 200428

Fast radio bursts (FRBs) are short pulses observed in the radio band from cosmological distances¹. One class of models invokes soft gamma-ray repeaters (SGRs), or magnetars, as the sources of FRBs². Some radio pulses have been observed from some magnetars³, but no FRB-like events have been detected in association with any magnetar burst, including one giant flare⁴. Recently, a pair of FRB-like bursts (termed FRB 200428) separated by 29 milliseconds were detected from the general direction of the Galactic magnetar SGR J1935+2154 (refs. ^5,6). Here, we report the detection of a non-thermal X-ray burst in the 1-250 keV energy band with the Insight-HXMT satellite⁷, which we identify as having been emitted from SGR J1935+2154. The burst showed two hard peaks with a separation of 34 milliseconds, broadly consistent with that of the two bursts in FRB 200428. The delay time between the double radio peak and the X-ray peaks is about 8.62 s, fully consistent with the dispersion delay of FRB 200428. We thus identify the non-thermal X-ray burst to be associated with FRB 200428, whose high-energy counterpart is the two hard X-ray peaks. Our results suggest that the non-thermal X-ray burst and FRB 200428 share the same physical origin in an explosive event from SGR J1935+2154.