{
  "id": "2311.13303",
  "version": "v1",
  "published": "2023-11-22T10:47:28.000Z",
  "updated": "2023-11-22T10:47:28.000Z",
  "title": "Discovery of torque reversal in the Be/X-ray binary pulsar GX 304-1",
  "authors": [
    "Amar Deo Chandra"
  ],
  "comment": "5 pages, 4 figures",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "We study the long-term spin period evolution of the Be/X-ray binary pulsar GX 304-1 and discover a new torque reversal after nearly three years of spinning up. The averaged spin-up rate before the torque reversal is $\\sim 1.3 \\times 10^{-13}$ Hz s$^{-1}$ which changes to an averaged spin-down rate of $\\sim -5 \\times 10^{-14}$ Hz s$^{-1}$. The pulsar is detected at low luminosities (about ${2}\\times 10^{35}$ erg s$^{-1}$) near periastron passages during the torque reversal suggesting that accretion is not quenched during this period. The long-term optical observations of the companion star suggest that the activity of the companion star may have decreased compared to the period when X-ray outbursts were earlier detected from the pulsar. The spin-up rates estimated during regular bright outbursts of the pulsar are observed to decrease systematically as the pulsar enters a low activity state after the outbursts and undergoes torque reversal. We explore plausible mechanisms to explain the torque reversal and long-term spin-down in this pulsar.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-11-22T10:47:28.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "be/x-ray binary pulsar gx",
      "torque reversal",
      "companion star",
      "spin-up rate",
      "long-term spin period evolution"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}