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A Spectroscopic Binary in the Hercules Dwarf Spheroidal Galaxy

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Author

Summary, in English

We present the radial velocity curve of a single-lined spectroscopic binary in the faint Hercules dwarf spheroidal (dSph) galaxy, based on 34 individual spectra covering more than 2 yr of observations. This is the first time that orbital elements could be derived for a binary in a dSph. The system consists of a metal-poor red giant and a low-mass companion, possibly a white dwarf, with a 135 day period in a moderately eccentric (e = 0.18) orbit. Its period and eccentricity are fully consistent with metal-poor binaries in the Galactic halo, while the projected semimajor axis is small, at a(p) sin i = 38 R-circle dot. In fact, a very close orbit could inhibit the production of heavier elements through s-process nucleosynthesis, leading to the very low abundances of neutron-capture elements that are found in this star. We discuss the further implications for the chemical enrichment history of the Hercules dSph, but find no compelling binary scenario that could reasonably explain the full, peculiar abundance pattern of the Hercules dSph galaxy.

Publishing year

2014

Language

English

Publication/Series

Astrophysical Journal

Volume

780

Issue

1

Document type

Journal article

Publisher

American Astronomical Society

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • binaries: spectroscopic
  • galaxies: dwarf
  • galaxies: evolution
  • galaxies:
  • individual (Hercules)
  • stars: abundances
  • stars: Population II

Status

Published

ISBN/ISSN/Other

  • ISSN: 0004-637X