Individual and averaged power density spectra of X-ray bursts from SGR J1935+2154: quasi-periodic oscillation search and slopes

• Published in: Monthly notices of the Royal Astronomical Society 2024-02, Vol.527 (4), p.11915-11924
• Main Authors: Xiao, Shuo, Li, Xiao-Bo, Xue, Wang-Chen, Xiong, Shao-Lin, Zhang, Shuang-Nan, Peng, Wen-Xi, Dong, Ai-Jun, Tuo, You-Li, Cai, Ce, Luo, Xi-Hong, Yang, Jiao-Jiao, Wang, Yue, Zheng, Chao, Zhang, Yan-Qiu, Liu, Jia-Cong, Tan, Wen-Jun, Wang, Chen-Wei, Wang, Ping, Li, Cheng-Kui, Yi, Shu-Xu, Dang, Shi-Jun, Shang, Lun-Hua, Zhao, Ru-shuang, Ma, Qing-Bo, Xie, Wei, Feng, Jian-Chao, Zhang, Bin, Zhang, Zhen, Ge, Ming-Yu, Zheng, Shi-Jie, Song, Li-Ming, Zhi, Qi-Jun
• Format: Article
• Language: English
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stae009

ABSTRACT The study of quasi-periodic oscillations (QPOs) and power density spectra (PDSs) continuum properties can help shed light on the still elusive emission physics of magnetars and as a window into the interiors of neutron stars using asteroseismology. In this work, we employ a PDS method to search for the QPOs in the hundreds of X-ray bursts from SGR J1935+2154 observed by Insight-HXMT, GECAM, and Fermi/GBM from 2014 July to 2022 January. Although no definitive QPO signal (significance >3 σ) is detected in individual bursts or the averaged periodogram of the bursts grouped by duration, we identify several bursts exhibiting features at ∼40 Hz, attributed to the the proximity intervals between adjacent pulses and consistent with that reported in the X-ray burst associated with FRB 200428. We investigate the PDS continuum properties and find that the distribution of the PDS slope in the simple power-law model peaks at ∼2.5, which is consistent with other magnetars but higher than 5/3 commonly seen in gamma-ray bursts. Besides, the distribution of the break frequency in the broken power-law model peaks at ∼60 Hz. Finally, we report that the power-law index of PDS has an anti-correlation and power-law dependence on the burst duration as well as the minimum variation time-scale.