A Spectroscopic Binary in the Hercules Dwarf Spheroidal Galaxy

Research output: Contribution to journalArticle

Abstract

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.

Details

Authors
Organisations
External organisations
  • Heidelberg University
  • University of Leicester
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology

Keywords

  • binaries: spectroscopic, galaxies: dwarf, galaxies: evolution, galaxies:, individual (Hercules), stars: abundances, stars: Population II
Original languageEnglish
JournalAstrophysical Journal
Volume780
Issue number1
Publication statusPublished - 2014
Publication categoryResearch
Peer-reviewedYes