{
  "id": "1805.01432",
  "version": "v1",
  "published": "2018-05-03T17:14:59.000Z",
  "updated": "2018-05-03T17:14:59.000Z",
  "title": "The circumstellar environment of HD50138 revealed by VLTI/AMBER at high angular resolution",
  "authors": [
    "M. Koutoulaki",
    "R. Garcia Lopez",
    "A. Natta",
    "A. Caratti o Garatti",
    "D. Coffey",
    "J. Sanchez-Bermudez",
    "T. P. Ray"
  ],
  "comment": "accepted for publication in A&A",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "HD50138 is a Herbig B[e] star with a circumstellar disc detected at IR and mm wavelength. Its brightness makes it a good candidate for NIR interferometry observations. We aim to resolve, spatially and spectrally, the continuum and hydrogen emission lines in the 2.12-2.47 micron region, to shed light on the immediate circumstellar environment of the star. VLTI/AMBER K-band observations provide spectra, visibilities, differential phases, and closure phases along three long baselines for the continuum, and HI emission in Br{\\gamma} and five high-n Pfund lines. By computing the pure-line visibilities, we derive the angular size of the different line-emitting regions. A simple LTE model was created to constrain the physical conditions of HI emitting region. The continuum region cannot be reproduced by a geometrical 2D elongated Gaussian fitting model. We estimate the size of the region to be 1 au. We find the Br{\\gamma} and Pfund lines come from a more compact region of size 0.4 au. The Br{\\gamma} line exhibits an S-shaped differential phase, indicative of rotation. The continuum and Br{\\gamma} line closure phase show offsets of $\\sim$-25$\\pm$5 $^o$ and 20$\\pm$10$^o$, respectively. This is evidence of an asymmetry in their origin, but with opposing directions. We find that we cannot converge on constraints for the HI physical parameters without a more detailed model. Our analysis reveals that HD50138 hosts a complex circumstellar environment. Its continuum emission cannot be reproduced by a simple disc brightness distribution. Similarly, several components must be evoked to reproduce the interferometric observables within the Br{\\gamma}, line. Combining the spectroscopic and interferometric data of the Br{\\gamma} and Pfund lines favours an origin in a wind region with a large opening angle. Finally, our results point to an evolved source.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2018-05-03T17:14:59.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "high angular resolution",
      "circumstellar environment",
      "pfund lines",
      "elongated gaussian fitting model",
      "vlti/amber"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}