Non-LTE modeling of the near-ultraviolet band of late-type stars

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Autor/in:
Erscheinungsjahr:
2009
Medientyp:
Text
Schlagworte:
  • Stars
  • Abundance
  • Carbon-enhanced metal-poor
  • Galaxies
  • Planets
  • stars: atmospheres
  • stars: late-type
  • stars: individual (Alpha Boo, Alpha CMi)
  • Sun: photosphere
  • Stars
  • Abundance
  • Carbon-enhanced metal-poor
  • Galaxies
  • Planets
Beschreibung:
  • We investigate the ability of both LTE and non-LTE (NLTE) models to fit the near-UV band absolute flux distribution, f λ(λ), and individual spectral line profiles of three standard stars for which high-quality spectrophotometry and high-resolution spectroscopy are available: The Sun (G2 V), Arcturus (K2 III), and Procyon (F5 IV-V). We investigate (1) the effect of the choice of atomic line list on the ability of NLTE models to fit the near-UV band f λ level, (2) the amount of a hypothesized continuous thermal absorption extinction source required to allow NLTE models to fit the observations, and (3) the semiempirical temperature structure, T kin(log τ5000), required to fit the observations with NLTE models and standard continuous near-UV extinction. We find that all models that are computed with high-quality atomic line lists predict too much flux in the near-UV band for Arcturus, but fit the warmer stars well. The variance among independent measurements of the solar irradiance in the near-UV is sufficiently large that we cannot definitely conclude that models predict too much near-UV flux, in contrast to other recent results. We surmise that the inadequacy of current atmospheric models of K giants in the near-UV band is best addressed by hypothesizing that there is still missing continuous thermal extinction, and that the missing near-UV extinction becomes more important with decreasing effective temperature for spectral classes later than early G, suggesting a molecular origin. © 2009. The American Astronomical Society. All rights reserved..
Lizenz:
  • info:eu-repo/semantics/openAccess
Quellsystem:
Forschungsinformationssystem der UHH
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oai:www.edit.fis.uni-hamburg.de:publications/a34d7d43-e4a7-4710-a440-aa9751a1ef68