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GHRS spectroscopy of chemically peculiar stars: The chi Lupi Pathfinder Project

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Author

  • DS Leckrone
  • Sveneric Johansson
  • Glenn Wahlgren
  • CR Proffitt
  • Tomas Brage

Summary, in English

The HST has provided visual images of the universe of unprecedented clarity and sensitivity. It is less widely known that the HST/GHRS has provided equally breathtaking views of a different kind Of "universe" - a "spectroscopic universe". Nowhere is this better seen than in the extraordinarily complex and beautiful ultraviolet spectrum of the ultra-sharp-lined, non-magnetic, chemically peculiar (CP) star chi Lupi (B9.5pHgMn + A2 Vm). We have begun a systematic exploration and quantitative analysis of this spectrum with the echelle mode of the GHRS. We call this the "The chi Lupi Pathfinder Project", because it is analogous to the exploration and mapping of a previously uncharted land by a diverse team of specialists - in this case astrophysicists and atomic physicists working synergistically. Our objective is to characterize, comprehensively and accurately, the full range of abundance and isotopic anomalies found in the atmosphere of at least one CP star to test and constrain the most widely accepted theoretical scenario for the production of abundance anomalies - radiatively-driven diffusion and gravitational settling. These physical mechanisms are important in several other astrophysical contexts. The surface layers of the CP stars provide a laboratory to investigate the conditions which foster them and the competing mechanisms which retard them. The GHRS echelle data set for chi Lupi covers 345 Angstrom, with S/N approximate to 50-100. We have quadrupled the number of elements for which abundances have been measured in this star, spanning most of the periodic table. These include several elements which have rarely, if ever, been seen before in a star other than the Sun and several examples of isotopically anomalous abundances. We have found systematic trends in these abundance data, which qualitatively support the mechanism of radiatively-driven diffusion and gravitational settling. However, our state-of-the-art theoretical, non-LTE diffusion models have not as yet been successful in sustaining the observed magnitudes of the largest abundance anomalies nor in reproducing anomalous isotope blends.

Publishing year

1998

Language

English

Pages

135-153

Publication/Series

The Scientific Impact of the Goddard High Resolution Spectrograph (Astronomical Society of the Pacific Conference Series)

Volume

143

Document type

Conference paper

Publisher

Astronomical Society of the Pacific (ASP)

Topic

  • Astronomy, Astrophysics and Cosmology

Conference name

Symposium on the Scientific Impact of the Goddard High Resolution Spectrograph

Conference date

1996-09-11 - 1996-09-12

Status

Published

ISBN/ISSN/Other

  • ISBN: 1-886733-63-5