Possible Periodic Windowed Behavior in SGR1935+2154 SGR Bursts

TL;DR

This study identifies a potential 231-day periodic windowed behavior in the soft gamma-ray bursts from SGR 1935+2154, suggesting a possible link between magnetar activity and repeating FRB sources.

Contribution

The paper presents evidence of a 231-day periodic windowed pattern in SGR 1935+2154's gamma-ray bursts, indicating a possible connection between magnetars and FRB mechanisms.

Findings

Detected a 231-day period with 55% window fraction.

Robustness of periodicity across different data subsets.

Simulations suggest the pattern is not due to random chance.

Abstract

Two repeating FRB sources, FRB180916 (CHIME/FRB Collaboration, 2020a) and FRB121102 (Rajwade, et al., 2020, Cruces, et al., 2021) display periodic windowed behavior (PWB) in the times of FRB detections. In PWB, events only occur within a periodic window spanning some fraction of the period, but no events may occur during many of the periods. During UT 2020 April 28, two peaks of a soft gamma burst (Li, et al., 2021) were identified with two FRB peaks (CHIME/FRB Collaboration, et al., 2020b) from soft gamma repeater (SGR) 1935+2154. As SGRs are a type of magnetar, these observations establish a link between at least some FRBs and magnetars. The analysis herein, which selects the period giving the minimum window fraction, shows PWB in this source's soft gamma-ray emission. For 161 bursts from 2014 through 2020 from IPN (Interplanetary Network) instruments, a clearly resolved minimum in window fraction vs. period occurs at a 231 +/- 9 day period, and 55 \% window fraction. The data cover only 6 bursting episodes, however, the periodicity result appears relatively robust: First, the IPN has excellent time coverage and is unlikely to miss bursts outside of these windows. Second, for various data subsets (with significantly less bursts), either the best or second best measured period was consistent with 231 days, even in the sub-sample with the richest bursting episode removed. In addition, simulations show that even small numbers of uniform random bursts do not show PWB, and that the results are not due to limited sampling. The apparent PWB could have alternative explanations; a firm conclusion of PWB would be evident, however, after the observation of more consistent episodes. If the periodicity of this SGR's bursts can be verified, and if similar behavior were observed in other repeating FRB sources, it might suggest a linkage between FRB and SGR burst mechanisms or emission conditions.