First results from the Goddard High-Resolution Spectrograph: Evidence for photospheric microturbulence in early O stars: Are surface gravities systematically underestimated?

I. Hubeny, S. R. Heap, B. Altner

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

GHRS spectra of two very hot stars (BD +75°325 and Melnick 42) provide evidence for the presence of microturbulence in their photospheres. In attempting to reproduce the observed spectra, we have built theoretical models in which the microturbulence is allowed to modify not only the Doppler line widths (classical "spectroscopic" microturbulence), but also the turbulent pressure (thus mimicking a "physical" turbulence). We find that a corresponding modification of the temperature-pressure stratification influences the hydrogen and helium line profiles to the extent that the surface gravities of early O stars determined without considering microturbulence are too low by 0.1-0.15 dex. Thus, including microturbulence would reduce, or resolve completely, a long-standing discrepancy between evolutionary and spectroscopic stellar masses.

Original languageEnglish (US)
Pages (from-to)L33-L36
JournalAstrophysical Journal
Volume377
Issue number1 PART II
DOIs
StatePublished - Jan 1 1991

Keywords

  • Stars: early-type
  • Stars: massive
  • Stars: subdwarfs
  • Stars: winds
  • Turbulence
  • Ultraviolet: spectra

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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