skip to main content

SciTech ConnectSciTech Connect

Title: New detections of arsenic, selenium, and other heavy elements in two metal-poor stars

We use the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope to obtain new high-quality spectra covering the 1900 ≤λ ≤ 2360 Å wavelength range for two metal-poor stars, HD 108317 and HD 128279. We derive abundances of Cu II, Zn II, As I, Se I, Mo II, and Cd II, which have not been detected previously in either star. Abundances derived for Ge I, Te I, Os II, and Pt I confirm those derived from lines at longer wavelengths. We also derive upper limits from the non-detection of W II, Hg II, Pb II, and Bi I. The mean [As/Fe] ratio derived from these two stars and five others in the literature is unchanged over the metallicity range –2.8 < [Fe/H] <–0.6, ([As/Fe]) = +0.28 ± 0.14 (σ = 0.36 dex). The mean [Se/Fe] ratio derived from these two stars and six others in the literature is also constant, ([Se/Fe]) = +0.16 ± 0.09 (σ = 0.26 dex). The As and Se abundances are enhanced relative to a simple extrapolation of the iron-peak abundances to higher masses, suggesting that this mass region (75 ≤A ≤ 82) may be the point at which a different nucleosynthetic mechanism beginsmore » to dominate the quasi-equilibrium α-rich freezeout of the iron peak. ([Cu II/Cu I]) = +0.56 ± 0.23 in HD 108317 and HD 128279, and we infer that lines of Cu I may not be formed in local thermodynamic equilibrium in these stars. The [Zn/Fe], [Mo/Fe], [Cd/Fe], and [Os/Fe] ratios are also derived from neutral and ionized species, and each ratio pair agrees within the mutual uncertainties, which range from 0.15 to 0.52 dex.« less
Authors:
 [1] ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8]
  1. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
  2. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
  3. Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)
  4. Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States)
  5. Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
  6. Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States)
  7. Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States)
  8. Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States)
Publication Date:
OSTI Identifier:
22365400
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 791; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ARSENIC; CADMIUM; COPPER; DETECTION; ELEMENT ABUNDANCE; EXTRAPOLATION; IRON; LTE; MASS; METALLICITY; MOLYBDENUM; NUCLEOSYNTHESIS; SELENIUM; SPACE; SPECTRA; STARS; TELESCOPES; WAVELENGTHS; ZINC