{
  "id": "2303.12542",
  "version": "v1",
  "published": "2023-03-22T13:18:23.000Z",
  "updated": "2023-03-22T13:18:23.000Z",
  "title": "Discovery of the linear energy-dependence of the spectral lag of X-ray bursts from SGR J1935+2154",
  "authors": [
    "Shuo Xiao",
    "You-Li Tuo",
    "Shuang-Nan Zhang",
    "Shao-Lin Xiong",
    "Lin Lin",
    "Yan-Qiu Zhang",
    "Yue Wang",
    "Wang-Chen Xue",
    "Ce Cai",
    "He Gao",
    "Cheng-Kui Li",
    "Xiao-Bo Li",
    "Chao Zheng",
    "Jia-Cong Liu",
    "Ping Wang",
    "Jin Wang",
    "Wen-Xi Peng",
    "Cong Zhan Liu",
    "Xin-Qiao Li",
    "Xiang-Yang Wen",
    "Zheng-Hua An",
    "Li-Ming Song",
    "Shi-Jie Zheng",
    "Fan Zhang",
    "Ai-Jun Dong",
    "Wei Xie",
    "Jian-Chao Feng",
    "Qing-Bo Ma",
    "De-Hua Wang",
    "Xi-Hong Luo",
    "Shi-Jun Dang",
    "Lun-Hua Shang",
    "Qi-Jun Zhi",
    "Ti-Pei Li"
  ],
  "comment": "accepted for publication in MNRAS",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "Spectral lag of the low-energy photons with respect to the high-energy ones is a common astrophysical phenomenon (such as Gamma-ray bursts and the Crab pulsar) and may serve as a key probe to the underlying radiation mechanism. However, spectral lag in keV range of the magnetar bursts has not been systematically studied yet. In this work, we perform a detailed spectral lag analysis with the Li-CCF method for SGR J1935+2154 bursts observed by {\\it Insight}-HXMT, GECAM and Fermi/GBM from July 2014 to Jan 2022. We discover that the spectral lags of about 61\\% (non-zero significance >1$\\sigma$) bursts from SGR J1935+2154 are linearly dependent on the photon energy ($E$) with $t_{\\rm lag}(E)=\\alpha (E/{\\rm keV})+C$, which may be explained by a linear change of the temperature of the blackbody-emitting plasma with time. The distribution of the slope ($\\alpha$) approximately follows a Gaussian function with mean and standard deviation of 0.02 ms/keV (i.e. high-energy photons arrive earlier) and 0.02 ms/keV, respectively. We also find that the distribution can be well fitted with three Gaussians with mean values of $\\sim$ -0.009, 0.013 and 0.039 ms/keV, which may correspond to different origins of the bursts. These spectral lag features may have important implications on the magnetar bursts.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-03-22T13:18:23.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "x-ray bursts",
      "linear energy-dependence",
      "magnetar bursts",
      "spectral lag features",
      "detailed spectral lag analysis"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}