{
  "id": "1909.04500",
  "version": "v1",
  "published": "2019-09-10T14:06:21.000Z",
  "updated": "2019-09-10T14:06:21.000Z",
  "title": "Radial pulsations of stars on the stage of the final helium flash",
  "authors": [
    "Yu. A. Fadeyev"
  ],
  "comment": "9 pages, 1 table, 7 figures, accepted for publication in Astronomy Letters",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "Stellar evolution calculations to the stage of the cooling white dwarf were done for population~I stars with masses on the main sequence $1M_\\odot\\le M_0\\le 1.5M_\\odot$. The final helium flash LTP is shown to occur in post--AGB stars with initial masses $1.3M_\\odot\\le M_0\\le 1.32M_\\odot$ for the overshooting parameter $f=0.016$. In the case of more effective overshooting ($f=0.018$) the final helium flash occurs at initial masses $1.28M_\\odot\\le M_0\\le 1.3M_\\odot$. Fivefold variations of the parameter responsible for the mass loss rate during the post--AGB stage do not affect occurrence of the final helium flash but lead to perceptible changes of the evolutionary time. Selected models of two evolutionary sequences with initial mass $M_0 = 1.3M_\\odot$ computed with overshooting parameters $f=0.016$ and $f=0.018$ were used as initial conditions in solution of the equations of hydrodynamics describing radial oscillations of stars on the stage of the final helium flash at effective temperatures less than $10^4$ K. The maximum pulsation period $\\Pi=117$ day determined for the evolutionary sequence $M_0=1.3M_\\odot$, $f=0.016$ is in a good agreement with observational estimates of the period of FG Sge. The mass, the radius and the effective temperature of the star are $M=0.565M_\\odot$, $R=126R_\\odot$ and $T_\\mathrm{eff}=4445$ K, respectively. At the same time the average period change rate of FG Sge from 1960 to 1990 is nearly three time larger than its theoretical estimate.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-09-10T14:06:21.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "radial pulsations",
      "initial mass",
      "final helium flash ltp",
      "final helium flash occurs",
      "fg sge"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 9,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}