Fig. 5: Absorbed X-ray pseudo-fluence distributions of X-ray transients from the distance of FRB 20200120E in the 0.5–10 keV energy range, compared with our best prompt X-ray fluence limit from FRB 20200120E.

The red, green, blue and orange histograms show the X-ray pseudo-fluence distributions of magnetar giant flares, magnetar intermediate flares, magnetar short bursts and type I X-ray bursts from LMXBs¹¹⁷, respectively. The vertical magenta line corresponds to our best prompt X-ray fluence limit from FRB 20200120E, derived from NICER observations at the time of burst B4. The X-ray fluence limit derived from XMM-Newton observations at the time of burst B9 is similar to the NICER X-ray fluence limit derived at the time of B4 (Table 1). The NICER X-ray fluence limit is only shown for clarity. The grey rectangle shows the range of X-ray pseudo-fluences derived from ULXBs detected from nearby galaxies^56,57,58. The vertical dashed black lines indicate the X-ray pseudo-fluences of GRBs believed to be associated with giant flares from extragalactic magnetars^{108,109,110,111,112,113}. The vertical dashed red line shows the predicted X-ray fluence of the X-ray burst associated with the FRB-like radio burst detected from SGR 1935+2154 on 28 April 2020¹², if it were emitted from the location of FRB 20200120E. The vertical dotted red line indicates the predicted X-ray fluence of burst B4, assuming the same X-ray-to-radio fluence ratio as the FRB-like radio burst detected on 28 April 2020 from SGR 1935+2154 (refs. ^8,9,12). The shaded brown region corresponds to the range of X-ray pseudo-fluences derived from bright type II X-ray bursts from GRO J1744–28 (ref. ¹¹⁴) and MXB 1730–335 (ref. ¹¹⁵), and X-ray flares resembling type II X-ray bursts from SMC X-1¹¹⁶. The vertical dotted purple line shows the X-ray pseudo-fluence of the flare predicted for burst B4 from FRB 20200120E, based on predictions from the relativistic shock model^26,27 (Methods and Supplementary Information). The X-ray pseudo-fluences were calculated using a distance of d = 3.63 ± 0.34 Mpc (ref. ¹²²) to FRB 20200120E.