Near-infrared H-band features in late O and B stars

M. M. Hanson, G. H. Rieke, K. L. Luhman

Research output: Contribution to journalArticle

43 Scopus citations

Abstract

We examine the spectral characteristics of normal OB stars with high-signal-to-noise ratio (>120) H-band (1.6 μm) spectra at a resolution of 2000. We find that several atomic lines vary smoothly with stellar temperature, as first shown by Blum et al. However, we find a previously unreported, significant variation in the strength of some of these lines with stellar luminosity. B supergiant stars show stronger He I and weaker Br II as compared with low-luminosity B dwarf stars of the same spectral class. It is for this reason that luminosity class must also be determined to obtain an accurate spectral type for a given star using H-band spectra. We suggest a method for estimating the spectral type and luminosity of an OB star over the wavelength range from 1.66 to 1.72 μm using hydrogen Br 11 at 1.681 μm, He I at 1.700 μm, and He 11 at 1.693 μm. The use of the near-infrared spectral range for classification has obvious advantages over optical classification when applied to heavily reddened stars, such as in starforming regions or deeply embedded lines of sight within the plane of the Galaxy, such as the Galactic center. Furthermore, the H band is less likely to be contaminated by infrared excess emission, which is frequently seen around massive young stellar objects beyond 2 μm.

Original languageEnglish (US)
Pages (from-to)1915-1921
Number of pages7
JournalAstronomical Journal
Volume116
Issue number4
DOIs
StatePublished - Oct 1998

Keywords

  • Atlases
  • Infrared radiation
  • Stars: early-type
  • Stars: fundamental parameters

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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