Reanalysis of the X-ray burst associated FRB 200428 with Insight-HXMT observations

TL;DR

This study reanalyzed the X-ray burst associated with FRB 200428 using Insight-HXMT data, improving timing and spectral measurements to better understand the physical origin of fast radio bursts.

Contribution

It reconstructed lost information from the saturated HXMT data, refining the timing and spectral analysis of the associated X-ray burst for the first time.

Findings

Precise timing of X-ray peaks relative to FRB 200428

Spectral analysis shows a cutoff power-law with ~60 keV cutoff energy

X-ray peaks are softer than the broader burst spectrum

Abstract

A double-peak X-ray burst from the Galactic magnetar SGR J1935+2154 was discovered as associated with the two radio pulses of FRB 200428 separated by 28.97+-0.02 ms. Precise measurements of the timing and spectral properties of the X-ray bursts are helpful for understanding the physical origin of fast radio bursts (FRBs). In this paper, we have reconstructed some information about the hard X-ray events, which were lost because the High Energy X-ray Telescope (HE) onboard the Insight-HXMT mission was saturated by this extremely bright burst, and used the information to improve the temporal and spectral analyses of the X-ray burst. The arrival times of the two X-ray peaks by fitting the new Insight-HXMT/HE lightcurve with multi-Gaussian profiles are 2.77+-0.45 ms and 34.30+-0.56 ms after the first peak of FRB 200428, respectively, while these two parameters are 2.57+-0.52 ms and 32.5+-1.4 ms if the fitting profile is a fast rise and exponential decay function. The spectrum of the two X-ray peaks could be described by a cutoff power-law with cutoff energy ~60 keV and photon index ~1.4, the latter is softer than that of the underlying bright and broader X-ray burst when the two X-ray peaks appeared.