Joint Observation of SGR J1935+2154 with Insight-HXMT and KM40m during the Active Episode of 2022 October

Abstract SGR J1935+2154 is the so-far unique magnetar from which fast radio bursts (FRBs) have been detected. In 2022 October, it resumed its burst activity, and we implemented a dedicated target-of-opportunity observation on it from 2022 October 13 to November 1 (about 940 ks in total) with Insight-HXMT, while the KM40m radio telescope has observed this source for about 1400 hr since October 15. We searched the data of Low Energy (LE), Medium Energy (ME), and High Energy (HE) X-ray telescopes onboard Insight-HXMT in the overlapping observation time windows with the KM40m radio telescope and revealed 60 magnetar X-ray bursts (MXBs), while KM40m only detected 1 radio burst. In particular, we find that there is an X-ray burst on October 21 (denoted as MXB 221021) temporally associated with this radio burst. Interestingly, this association event shows very different morphology from the X-ray and radio association events from this source reported before (e.g., MXB/FRB 200428). Moreover, we systematically analyzed the temporal and spectral properties of the sample of MXBs during this observation and found that the (radio-associated) MXB 221021 shows some different properties from other MXBs without associated radio bursts. These findings shed new light on the physical mechanisms of X-ray bursts and radio burst emission in magnetars.