Log-Gaussian Distribution and Evolution of Minimum Variation Timescales for SGR J1550-5418

• Published in: The Astrophysical journal Vol. 967; no. 2; pp. 128 - 138
• Main Authors: Xiao, Shuo, Zhang, Yan-Ting, Yang, Jiao-Jiao, Hong, Mei-Xin, Liao, Tong-Lei, Luo, Xi-Hong
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.06.2024; IOP Publishing
• Subjects: Evolution; Magnetars; Magnetic fields; Normal distribution; Radio bursts; Topology; X-ray bursts
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ad43e0

The major observation of the X-ray burst (XRB) in association with the fast radio burst (FRB) FRB 200428 originating from SGR J1935+2154 on 2020 April 28 substantiates magnetars as one of the origins of FRBs. However, it is still unclear why only a few XRBs in association with FRBs have been observed solely in this magnetar. In this study, we investigate the minimum variation timescales (MVTs) of XRBs from SGR J1550-5418, an active magnetar similar to SGR J1935+2154, and conduct a comprehensive comparison of their MVT properties. Our analysis reveals that the distribution of the MVT for SGR J1550-5418 follows a lognormal Gaussian function with the mean 6.4 ± 0.4 ms. Interestingly, we detect an evolution in the MVTs, i.e., the fitted mean of the MVT distribution in 2008 October is about 3 times larger than that in 2009, indicating potential variations in radiation regions possibly attributed to changes in magnetic field topology. Besides, we do not find a significant correlation between the MVT and either duration or energy. Finally, there is no significant difference between the MVT distributions across different energy ranges for SGR J1550-5418 and SGR J1935+2154, which supports a common physical origin.