{
  "id": "1604.06701",
  "version": "v1",
  "published": "2016-04-22T15:11:15.000Z",
  "updated": "2016-04-22T15:11:15.000Z",
  "title": "On the nature of magnetic cycles at different ages of stars",
  "authors": [
    "K. Oláh",
    "Zs. Kővári",
    "K. Petrovay",
    "W. Soon",
    "S. Baliunas",
    "Z. Kolláth",
    "K. Vida"
  ],
  "comment": "Accepted to Astronomy and Astrophysics",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "We study the different patterns of interannual magnetic variability in stars on or near the lower main sequence, approximately solar-type (G-K dwarf) stars in time series of 36 years from the Mount Wilson Observatory Ca\\,{\\sc ii}\\,H\\&K survey. Our main aim is to search for correlations between cycles, activity measures and ages. Time-frequency analysis has been used to discern and reveal patterns and morphology of stellar activity cycles, including multiple and changing cycles, in the datasets. Both the results from short-term Fourier transform and its refinement using the Choi-Williams distribution, with better frequency resolution, are presented in this study. Rotational periods of the stars were derived using multi-frequency Fourier analysis.From the studied 29 stars we found at least one activity cycle on 28 of them. Twelve stars, with longer rotational periods ($39.7\\pm6.0$ days) have simple, smooth cycles, and the rest of the stars, with on-average much faster rotation ($18.1\\pm12.2$ days) show complex and sometimes vigorously changing, multiple cycles. The cycles are longer and quite uniform in the first group ($9.7\\pm1.9$ years), while are generally shorter and with greater variety in the second one ($7.6\\pm4.9$). There is a clear age division between stars with smooth and complex cycles that follows the known separation between the older and younger stars at around 2 to 3~Gyr of age.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-04-22T15:11:15.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "magnetic cycles",
      "longer rotational periods",
      "interannual magnetic variability",
      "clear age division",
      "multi-frequency fourier analysis"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2016arXiv160406701O"
    }
  }
}