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Mercury in the HgMn stars chi Lupi and HR 7775

På svenska

Author

  • CR Proffitt
  • Tomas Brage
  • DS Leckrone
  • Glenn Wahlgren
  • JC Brandt
  • CJ Sansonetti
  • J Reader
  • Sveneric Johansson

Summary, in English

Observations of mercury lines in the HgMn stars chi Lupi and HR 7775 made with the Hubble Space Telescope Goddard High Resolution Spectrograph are presented and analyzed. In chi Lupi we find that all observed lines are consistent with the same isotopic mixture (essentially pure (204)Hg). Strong ionization anomalies are present, with UV Hg I lines being too weak and Hg III lines too strong for the abundance derived from lines of the majority ionization state, Hg rr. Observations of mercury in I;IR 7775 show less extreme isotope and ionization anomalies. We find that the ionization anomaly in the Hg I resonance lines can be plausibly explained as a non-LTE effect, but the same non-LTE calculations show that the Hg III ionization anomaly in chi Lupi cannot be explained in this way. Radiative force calculations show that the observed mercury abundance cannot be supported in the atmosphere by the radiative forces alone. We suggest that weak mixing brings mercury into the line-forming region from below the photosphere, while a wind of order 10(-14) M. yr(-1) supports a cloud of Hg III at very small optical depths.

Publishing year

1999

Language

English

Pages

942-960

Publication/Series

Astrophysical Journal

Volume

512

Issue

2

Document type

Journal article

Publisher

American Astronomical Society

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • HR 7775)
  • stars : peculiar
  • stars : individual (chi Lupi
  • diffusion
  • stars : abundances

Status

Published

ISBN/ISSN/Other

  • ISSN: 0004-637X