A spectroscopic binary in the Hercules dwarf spheroidal galaxy

Journal Article · Wed Jan 01 00:00:00 EST 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/780/1/91· OSTI ID:22348306

Koch, Andreas; Hansen, Terese ^[1]; Feltzing, Sofia ^[2]

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1. Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, D-69117 Heidelberg (Germany)
2. Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-22100 Lund (Sweden)

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{sub p} sin i = 38 R {sub ☉}. 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.

• OSTI ID: 22348306
• Journal Information: Astrophysical Journal, Vol. 780, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
BINARY STARS
CAPTURE
COVERINGS
GALAXIES
MASS
METALS
NEUTRON REACTIONS
NUCLEOSYNTHESIS
ORBITS
RADIAL VELOCITY
S PROCESS
SPECTRA
SPHERICAL CONFIGURATION
WHITE DWARF STARS