{
  "id": "1302.4684",
  "version": "v1",
  "published": "2013-02-19T17:19:34.000Z",
  "updated": "2013-02-19T17:19:34.000Z",
  "title": "Polarimetric observations of $σ$ Orionis E",
  "authors": [
    "Alex C. Carciofi",
    "Daniel M. Faes",
    "Richard H. D. Townsend",
    "Jon E Bjorkman"
  ],
  "comment": "5 pages, 4 figures, accepted for The Astrophysical Journal Letters",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "Some massive stars possess strong magnetic fields that confine plasma in the circumstellar environment. These \\textit{magnetospheres} have been studied spectroscopically, photometrically and, more recently, interferometrically. Here we report on the first firm detection of a magnetosphere in continuum linear polarization, as a result of monitoring of $\\sigma$\\,Ori\\,E at the Pico dos Dias Observatory. {The non-zero intrinsic polarization indicates an asymmetric structure, whose minor elongation axis is oriented $150\\fdg0$ east of the celestial north.} A modulation of the polarization was observed, with a period of half of the rotation period, which supports the theoretical prediction of the presence of two diametrally opposed, co-rotating blobs of gas. A phase lag of -0.085 was detected between the polarization minimum and the primary minimum of the light curve, suggestive of a complex shape of the plasma clouds. We present a preliminary analysis of the data with the Rigidly Rotating Magnetosphere model, which could not reproduce simultaneously the photometric and polarimetric data. A toy model comprising two spherical co-rotating blobs {joined by a thin disk} proved more successful in reproducing the polarization modulation. {With this model we were able to determine that the total scattering mass of the thin disk is similar to the mass of the blobs ($2M_{\\rm b}/M_{\\rm d}=1.2$) and that the blobs are rotating counterclockwise on the plane of the sky.} This result shows that polarimetry can provide a diagnostic of the geometry of clouds, which will serve as an important constraint for {improving} the Rigidly Rotating Magnetosphere model.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2013-02-19T17:19:34.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "polarimetric observations",
      "rigidly rotating magnetosphere model",
      "stars possess strong magnetic fields",
      "polarization",
      "massive stars possess strong magnetic"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/2041-8205/766/1/L9",
      "journal": "The Astrophysical Journal",
      "year": 2013,
      "month": "Mar",
      "volume": 766,
      "number": 1
    },
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1220226,
      "adsabs": "2013ApJ...766L...9C"
    }
  }
}