{
  "id": "2501.04542",
  "version": "v1",
  "published": "2025-01-08T14:44:55.000Z",
  "updated": "2025-01-08T14:44:55.000Z",
  "title": "Spectral Study of Aql~X-1 during \\textit{Pulse-on} and \\textit{Pulse-off} Stages",
  "authors": [
    "T. Kocabıyık",
    "C. Güngör",
    "M. T. Sağlam",
    "T. Güver",
    "Z. F. Bostancı"
  ],
  "comment": "Accepted for publication in MNRAS. 7 Pages, 4 Figures",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "We present a detailed spectral study of an intermittent-AMXP Aql X-1 during the \\textit{pulse-on} and \\textit{pulse-off} stages by using the archival RXTE data. We first perform temporal analysis by using Z$_n^2$ technique in three different energy bands, 3.0 -- 13.0~keV, 13.0 -- 23.0~keV and 23.0 -- 33.0~keV, for the last 128~s time segment of the RXTE data including \\textit{pulse-on} region. We show that the pulse is the most significant in the softest band. We, then, show that the spectrum is represented the best via combination of absorbed blackbody, disk blackbody and a gaussian line. We modeled the last four segments of the data 30188-03-05-00 to better compare \\textit{pulse-on} and \\textit{pulse-off} stages. We found a vague residual in the spectral fit of the \\textit{pulse-on} segment between $\\sim$3.0 -- 13.0~keV which agrees with the result of temporal analysis. We show that the residual may be represented with an extra blackbody component with the temperature of 1.75~keV and the radius of 0.75$\\pm$0.49 km. For deeper analysis, we performed phase-resolved spectroscopy to the last 128~s, \\textit{pulse-on}, segment. We obtain two separate spectra for the spin phase range of 0.75 -- 0.25, \\textit{pulse-high} and 0.25 -- 0.75, \\textit{pulse-low} and followed the same procedure. We display that the residual becomes more clear for \\textit{pulse-high} compared to the \\textit{pulse-low}. We report that the additional blackbody component, which models the residual, indicates a hotspot from the surface of the neutron star with the radius of 1.65$\\pm$0.74 km whose temperature is 1.65 keV.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2025-01-08T14:44:55.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "spectral study",
      "first perform temporal analysis",
      "archival rxte data",
      "additional blackbody component",
      "extra blackbody component"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 7,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}