{
  "id": "1211.6091",
  "version": "v1",
  "published": "2012-11-26T20:54:23.000Z",
  "updated": "2012-11-26T20:54:23.000Z",
  "title": "H-alpha Activity of Old M Dwarfs: Stellar Cycles and Mean Activity Levels For 93 Low-Mass Stars in the Solar Neighborhood",
  "authors": [
    "Paul Robertson",
    "Michael Endl",
    "William D. Cochran",
    "Sarah E. Dodson-Robinson"
  ],
  "comment": "Submitted to ApJ. Reflects comments from a positive referee",
  "categories": [
    "astro-ph.SR",
    "astro-ph.EP"
  ],
  "abstract": "Through the McDonald Observatory M Dwarf Planet Search, we have acquired nearly 3,000 high-resolution spectra of 93 late-type (K5-M5) stars over more than a decade using HET/HRS. This sample provides a unique opportunity to investigate the occurrence of long-term stellar activity cycles for low-mass stars. In this paper, we examine the stellar activity of our targets as reflected in the H-alpha feature. We have identified periodic signals for 6 stars, with periods ranging from days to more than 10 years, and find long-term trends for 7 others. Stellar cycles with P > 1 year are present for at least 5% of our targets. Additionally, we present an analysis of the time-averaged activity levels of our sample, and search for correlations with other stellar properties. In particular, we find that more massive, earlier type (M0-M2) stars tend to be more active than later type dwarfs. Furthermore, high-metallicity stars tend to be more active at a given stellar mass. We also evaluate H-alpha variability as a tracer of activity-induced radial velocity (RV) variation. For the M dwarf GJ 1170, H-alpha variation reveals stellar activity patterns matching those seen in the RVs, mimicking the signal of a giant planet, and we find evidence that the previously identified stellar activity cycle of GJ 581 may be responsible for the recently retracted planet f (Vogt et al. 2012) in that system. In general, though, we find that H-alpha is not frequently correlated with RV at the precision (typically 6-7 m/s) of our measurements.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2012-11-26T20:54:23.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "mean activity levels",
      "stellar cycles",
      "low-mass stars",
      "h-alpha activity",
      "solar neighborhood"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/0004-637X/764/1/3",
      "journal": "The Astrophysical Journal",
      "year": 2013,
      "month": "Feb",
      "volume": 764,
      "number": 1,
      "pages": 3
    },
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1203818,
      "adsabs": "2013ApJ...764....3R"
    }
  }
}