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Title: Neutron-capture nucleosynthesis in the first stars

Recent studies suggest that metal-poor stars enhanced in carbon but containing low levels of neutron-capture elements may have been among the first to incorporate the nucleosynthesis products of the first generation of stars. We have observed 16 stars with enhanced carbon or nitrogen using the MIKE Spectrograph on the Magellan Telescopes at Las Campanas Observatory and the Tull Spectrograph on the Smith Telescope at McDonald Observatory. We present radial velocities, stellar parameters, and detailed abundance patterns for these stars. Strontium, yttrium, zirconium, barium, europium, ytterbium, and other heavy elements are detected. In four stars, these heavy elements appear to have originated in some form of r-process nucleosynthesis. In one star, a partial s-process origin is possible. The origin of the heavy elements in the rest of the sample cannot be determined unambiguously. The presence of elements heavier than the iron group offers further evidence that zero-metallicity rapidly rotating massive stars and pair instability supernovae did not contribute substantial amounts of neutron-capture elements to the regions where the stars in our sample formed. If the carbon- or nitrogen-enhanced metal-poor stars with low levels of neutron-capture elements were enriched by products of zero-metallicity supernovae only, then the presence of these heavy elementsmore » indicates that at least one form of neutron-capture reaction operated in some of the first stars.« less
Authors:
 [1] ; ; ;  [2] ;  [3]
  1. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
  2. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
  3. Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712 (United States)
Publication Date:
OSTI Identifier:
22357226
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 784; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; BY-PRODUCTS; CARBON; EUROPIUM; INSTABILITY; IRON; LANTHANUM SULFIDES; NEUTRON REACTIONS; NUCLEOSYNTHESIS; R PROCESS; RADIAL VELOCITY; S PROCESS; STRONTIUM; SUPERNOVAE; TELESCOPES; YTTERBIUM; YTTRIUM; ZIRCONIUM