Insight-HXMT dedicated 33-day observation of SGR J1935+2154 II. Burst Spectral Catalog

TL;DR

This study presents a detailed spectral catalog of 75 bursts from magnetar SGR J1935+2154 observed over 33 days by Insight-HXMT, revealing spectral characteristics, distribution patterns, and a notable burst related to FRB 200428.

Contribution

It provides the first comprehensive spectral analysis of SGR J1935+2154 bursts during a dedicated observation period, highlighting spectral preferences and distribution similarities with other detectors.

Findings

15% of bursts favor the CPL spectral model.

Burst fluence distribution follows a power law similar to Fermi/GBM.

A burst with similar peak energy to the FRB 200428-associated burst was identified.

Abstract

Since April 28, 2020, Insight-HXMT has implemented a dedicated observation on the magnetar SGR J1935+2154. Thanks to the wide energy band (1-250 keV) and high sensitivity of Insight-HXMT, we obtained 75 bursts from SGR J1935+2154 during a month-long activity episode after the emission of FRB 200428. Here, we report the detailed time-integrated spectral analysis of these bursts and the statistical distribution of the spectral parameters. We find that for 15%(11/75) of SGR J1935+2154 bursts, the CPL model is preferred, and most of them occurred in the latter part of this active epoch. In the cumulative fluence distribution, we find that the fluence of bursts in our sample is about an order of magnitude weaker than that of Fermi/GBM, but follows the same power law distribution. Finally, we find a burst with similar peak energy to the time-integrated spectrum of the X-ray burst associated with FRB 200428 (FRB 200428-Associated Burst), but the low energy index is harder.