{
  "id": "2403.09595",
  "version": "v1",
  "published": "2024-03-14T17:35:57.000Z",
  "updated": "2024-03-14T17:35:57.000Z",
  "title": "A comprehensive study of orbital evolution of LMC X-4: Existence of a second derivative of the orbital period",
  "authors": [
    "Chetana Jain",
    "Rahul Sharma",
    "Biswajit Paul"
  ],
  "comment": "Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal",
  "categories": [
    "astro-ph.HE",
    "astro-ph.SR"
  ],
  "abstract": "We report here results from pulse arrival time delay analysis of the eclipsing high mass X-ray binary pulsar LMC X-4 using observations made with the Rossi X-ray Timing Explorer, XMM-Newton, NuSTAR and AstroSat. Combining the orbital parameters determined from these observations with the historical measurements dating back to 1998, we have extended the $T_{\\pi/2}$ epoch history of LMC X-4 by about 4600 binary orbits spanning about 18 years. We also report mid-eclipse time measurements ($T_{ecl}$) using data obtained from wide-field X-ray monitors of MAXI-GSC and Swift-BAT. Combining the new $T_{\\pi/2}$ and $T_{ecl}$ estimates with all the previously reported values, we have significantly improved the orbital evolution measurement, which indicates that the orbital period is evolving at a time scale ($P_{\\rm orb}/\\dot{P}_{\\rm orb}$ ) of about 0.8 Myr. For the first time in an accreting X-ray pulsar system, we confirm the existence of a second derivative of the orbital period, having an evolution time scale ($\\dot{P}_{orb}/\\ddot{P}_{orb}$) of about 55 yr. Detection of a second derivative of the orbital period in LMC X-4 makes its orbital evolution timescale more uncertain, which may also be true for other HMXBs. Independent solutions for the orbital evolution measurement using the mid-eclipse data and the pulse timing data are consistent with each other, and help us put an upper limit of 0.009 on the eccentricity of the binary system.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-03-14T17:35:57.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "orbital period",
      "second derivative",
      "high mass x-ray binary",
      "x-ray binary pulsar lmc",
      "mass x-ray binary pulsar"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}