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.

快速射电暴 (FRB) 是从宇宙学距离¹在射电波段观察到的短脉冲。一类模型调用软伽马射线中继器 (SGR) 或磁星作为快速射电暴²的来源。^{从一些磁星3}中观察到了一些无线电脉冲，但没有检测到与任何磁星爆发相关的类似 FRB 的事件，包括一次巨大的耀斑⁴。^{最近，从银河磁星 SGR J1935+2154（参考文献5,6} ）的大致方向检测到一对相隔 29 毫秒的 FRB 状爆发（称为 FRB 200428 ）。^{在这里，我们报告了使用 Insight-HXMT 卫星7}在 1-250 keV 能带中检测到非热 X 射线爆发，我们确定它是从 SGR J1935+2154 发出的。爆发出现两个相隔34毫秒的硬峰，与FRB 200428中的两次爆发大体一致。双射电波峰与X射线峰之间的延迟时间约为8.62 s，与色散延迟完全一致的 FRB 200428。因此，我们确定与 FRB 200428 相关的非热 X 射线爆发，其高能对应物是两个硬 X 射线峰。我们的结果表明，非热 X 射线爆发和 FRB 200428 在 SGR J1935+2154 的爆炸事件中具有相同的物理起源。