{
  "id": "2412.07863",
  "version": "v1",
  "published": "2024-12-10T19:10:19.000Z",
  "updated": "2024-12-10T19:10:19.000Z",
  "title": "Accretion onto WD 2226$-$210, the central star of the Helix Nebula",
  "authors": [
    "S. Estrada-Dorado",
    "M. A. Guerrero",
    "J. A. Toalá",
    "R. F. Maldonado",
    "V. Lora",
    "D. A. Vasquez-Torres",
    "Y. -H. Chu"
  ],
  "comment": "8 pages, 3 figures, 3 tables; accepted to MNRAS",
  "categories": [
    "astro-ph.SR",
    "astro-ph.HE"
  ],
  "abstract": "The central star of the Helix Nebula, WD 2226$-$210 presents enigmatic hard X-ray emission and mid-IR excess. The latter has been attributed to a dusty disk or a cloud-like structure around WD 2226$-$210 formed from material of Kuiper Belt-like or comet-like objects in highly eccentric orbits. We present here a detailed analysis of multi-epoch Chandra and XMM-Newton X-ray observations of WD 2226$-$210, comparing these to previous Einstein and ROSAT data. The luminosity of the hard X-ray component of WD 2226$-$210 has remained basically constant in the decade from 1992 to 2002, with very subtle evidence for variability in timescales of hours. Under the assumption that the X-ray emission from WD 2226$-$210 is due to accretion of material, an accretion rate of $\\dot{M}\\approx10^{-10}$ M$_\\odot$ yr$^{-1}$ is estimated. The origin of the material accreted by WD 2226$-$210 is uncertain, and can be attributed to the disk-like structure around it or to a sub-stellar donor companion. The accretion rate proposed for the continuous replenishment by bombardment of the mid-IR-emitting structure around WD 2226$-$210 cannot match that required by the X-ray emission.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-12-10T19:10:19.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "central star",
      "helix nebula",
      "accretion rate",
      "enigmatic hard x-ray emission",
      "sub-stellar donor companion"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 8,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}