The Minimum Variation Timescales of X-Ray Bursts from SGR J1935+2154

Abstract The minimum variation timescale (MVT) of soft gamma-ray repeaters can be an important probe to estimate the emission region in pulsar-like models, as well Lorentz factor and radius possible relativistic jet burst (GRB)–like thus revealing their progenitors physical mechanisms. In this work, we systematically study MVTs hundreds X-ray bursts (XRBs) from SGR J1935+2154 observed by Insight-HXMT, GECAM, Fermi/Gamma-ray Burst Monitor 2014 July 2022 January through Bayesian block algorithm. We find that peak at ∼2 ms, corresponding a light-travel time size about 600 km, which supports magnetospheric origin models. shock are also constrained GRB-like Interestingly, MVT XRB associated with FRB 200428 is ∼70 longer than most implies its special radiation mechanism. addition, median 7 shorter 40 ms 480 for short GRBs or long GRBs, respectively. However, independent duration, similar GRBs. Finally, investigate energy dependence suggest there marginal evidence power-law relationship like but rate least order magnitude smaller. These features may provide approach identify magnetar origin.