{
  "id": "0911.0424",
  "version": "v1",
  "published": "2009-11-02T21:01:24.000Z",
  "updated": "2009-11-02T21:01:24.000Z",
  "title": "The Origin of Enhanced Activity in the Suns of M67",
  "authors": [
    "Ansgar Reiners",
    "Mark S. Giampapa"
  ],
  "comment": "accepted by ApJ",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "We report the results of the analysis of high resolution photospheric line spectra obtained with the UVES instrument on the VLT for a sample of 15 solar-type stars selected from a recent survey of the distribution of H and K chromospheric line strengths in the solar-age open cluster M67. We find upper limits to the projected rotation velocities that are consistent with solar-like rotation (i.e., v sini ~< 2-3 km/s) for objects with Ca II chromospheric activity within the range of the contemporary solar cycle. Two solar-type stars in our sample exhibit chromospheric emission well in excess of even solar maximum values. In one case, Sanders 1452, we measure a minimum rotational velocity of vsini = 4 +/- 0.5 km/s, or over twice the solar equatorial rotational velocity. The other star with enhanced activity, Sanders 747, is a spectroscopic binary. We conclude that high activity in solar-type stars in M67 that exceeds solar levels is likely due to more rapid rotation rather than an excursion in solar-like activity cycles to unusually high levels. We estimate an upper limit of 0.2% for the range of brightness changes occurring as a result of chromospheric activity in solar-type stars and, by inference, in the Sun itself. We discuss possible implications for our understanding of angular momentum evolution in solar-type stars, and we tentatively attribute the rapid rotation in Sanders 1452 to a reduced braking efficiency.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2009-11-02T21:01:24.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "solar-type stars",
      "enhanced activity",
      "high resolution photospheric line spectra",
      "rapid rotation",
      "upper limit"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/0004-637X/707/1/852",
      "journal": "The Astrophysical Journal",
      "year": 2009,
      "month": "Dec",
      "volume": 707,
      "number": 1,
      "pages": 852
    },
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 835838,
      "adsabs": "2009ApJ...707..852R"
    }
  }
}