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A Spectroscopic Binary in the Hercules Dwarf Spheroidal Galaxy

Koch, Andreas; Hansen, Terese; Feltzing, Sofia LU and Wilkinson, Mark I. (2014) In Astrophysical Journal 780(1).
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
binaries: spectroscopic, galaxies: dwarf, galaxies: evolution, galaxies:, individual (Hercules), stars: abundances, stars: Population II
in
Astrophysical Journal
volume
780
issue
1
publisher
University of Chicago Press
external identifiers
  • wos:000328937100091
  • scopus:84890500856
ISSN
0004-637X
DOI
10.1088/0004-637X/780/1/91
language
English
LU publication?
yes
id
aa64a458-b385-4847-a79c-4b665fe1c9d1 (old id 4327025)
date added to LUP
2014-03-03 08:56:31
date last changed
2017-05-21 03:59:53
@article{aa64a458-b385-4847-a79c-4b665fe1c9d1,
  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.},
  author       = {Koch, Andreas and Hansen, Terese and Feltzing, Sofia and Wilkinson, Mark I.},
  issn         = {0004-637X},
  keyword      = {binaries: spectroscopic,galaxies: dwarf,galaxies: evolution,galaxies:,individual (Hercules),stars: abundances,stars: Population II},
  language     = {eng},
  number       = {1},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {A Spectroscopic Binary in the Hercules Dwarf Spheroidal Galaxy},
  url          = {http://dx.doi.org/10.1088/0004-637X/780/1/91},
  volume       = {780},
  year         = {2014},
}