{
  "id": "2010.14311",
  "version": "v1",
  "published": "2020-10-27T14:12:54.000Z",
  "updated": "2020-10-27T14:12:54.000Z",
  "title": "The large-scale magnetic field of Proxima Centauri near activity maximum",
  "authors": [
    "Baptiste Klein",
    "Jean-François Donati",
    "Élodie M. Hébrard",
    "Bonnie Zaire",
    "Colin P. Folsom",
    "Julien Morin",
    "Xavier Delfosse",
    "Xavier Bonfils"
  ],
  "comment": "7 pages, 5 figures, accepted to MNRAS",
  "categories": [
    "astro-ph.SR",
    "astro-ph.EP"
  ],
  "abstract": "We report the detection of a large-scale magnetic field at the surface of the slowly-rotating fully-convective M dwarf Proxima Centauri. Ten circular polarization spectra, collected from April to July 2017 with the HARPS-Pol spectropolarimeter, exhibit rotationally-modulated Zeeman signatures suggesting a stellar rotation period of $89.8 \\pm 4.0$ d. Using Zeeman-Doppler Imaging, we invert the circular polarization spectra into a surface distribution of the large-scale magnetic field. We find that Proxima Cen hosts a large-scale magnetic field of typical strength 200 G, whose topology is mainly poloidal, and moderately axisymmetric, featuring, in particular, a dipole component of 135 G tilted at 51$^{\\circ}$ to the rotation axis. The large-scale magnetic flux is roughly 3 times smaller than the flux measured from the Zeeman broadening of unpolarized lines, which suggests that the underlying dynamo is efficient at generating a magnetic field at the largest spatial scales. Our observations occur $\\sim$1 yr after the maximum of the reported 7 yr-activity cycle of Proxima Cen, which opens the door for the first long-term study of how the large-scale field evolves with the magnetic cycle in a fully-convective very-low-mass star. Finally, we find that Proxima Cen's habitable zone planet, Proxima-b, is likely orbiting outside the Alfv\\`en surface, where no direct magnetic star-planet interactions occur.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-10-27T14:12:54.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "large-scale magnetic field",
      "proxima centauri",
      "activity maximum",
      "cens habitable zone planet",
      "circular polarization spectra"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 7,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}