New insight into the Rapid Burster by Insight-HXMT

TL;DR

This study analyzes type II X-ray bursts from the Rapid Burster using Insight-HXMT and Swift/XRT, revealing a 3-second hard X-ray lag in long bursts and suggesting a non-thermal spectrum, providing new insights into burst mechanisms.

Contribution

First detection of a 3-second hard X-ray lag in long-duration bursts from the Rapid Burster, indicating a possible temporally evolving corona.

Findings

Hard X-ray lag of 3 seconds in long bursts

Non-thermal energy spectrum across bursts

Potential evidence for a temporally evolving corona

Abstract

We report the timing and spectral analyses upon of the type II X-ray bursts from the Rapid Burster (MXB 1730--335) observed by Insight-HXMT and Swift/XRT. By stacking the long-duration bursts, we find for the first time that the hard X-rays are lagging than the soft X-rays by 3 seconds. However, such a lag is not visible for the short-duration bursts, probably because of the poor statistics. For all bursts the energy spectrum is found to be non-thermal, thanks to the broad band coverage of Insight-HXMT. These findings put new insights into the type-II bursts and require a temporally showing-up corona for possible interpretation.