Abundances of Sr, Y, and Zr in Metal-Poor Stars and Implications for Chemical Evolution in the Early Galaxy

Abstract

Studies of nucleosynthesis in neutrino-driven winds from nascent neutron stars show that the elements from Sr through Ag with mass numbers A~88-110 are produced by charged-particle reactions (CPR) during the alpha-process in the winds. Accordingly, we have attributed all these elements in stars of low metallicities ([Fe/H]<-1.5) to low-mass and normal supernovae (SNe) from progenitors of ~8-11M_sun and ~12-25M_sun, respectively, which leave behind neutron stars. Using this rule and attributing all Fe production to normal SNe, we previously developed a phenomenological two-component model, which predicts that [Sr/Fe]>-0.32 for all metal-poor stars. The high-resolution data now available on Sr abundances in Galactic halo stars show that there is a great shortfall of Sr relative to Fe in many stars with [Fe/H]<-3. This is in direct conflict with the above prediction. The same conflict also exists for two other CPR elements Y and Zr. The very low abundances of Sr, Y, and Zr observed in stars with [Fe/H]<-3 thus require a stellar source that cannot be low-mass or normal SNe. We show that this observation requires a stellar source leaving behind black holes and that hypernovae (HNe) from progenitors of ~25-50M_sun are the most plausible candidates. (Abridged)

42 pages, 8 figures, to appear in ApJ

References in corpus (11)

• Nucleosynthetic signatures of the first stars
• First Stars VIII -- Enrichment of the neutron-capture elements in the early Galaxy
• Population III star formation in a Lambda CDM universe, I: The effect of formation redshift and environment on protostellar accretion rate
• HE 0557-4840 - Ultra-Metal-Poor and Carbon-Rich
• Neutron-capture elements in the very metal-poor star HD122563
• New Extremely Metal-Poor Stars in the Galactic Halo
• Dynamics of shock propagation and nucleosynthesis conditions in O-Ne-Mg core supernovae
• The first generation of stars in LCDM cosmology
• Chemical Abundance Analysis of the Extremely Metal-Poor Star HE 1300+0157
• A New Type of Extremely Metal Poor Star
• r-Process Nucleosynthesis in Shocked Surface Layers of O-Ne-Mg Cores

Cited by in corpus (28)

• Stellar Abundances in the Solar Neighborhood: The Hypatia Catalog
• Production of Light Element Primary Process nuclei in neutrino-driven winds
• The Chemical Evolution of the Draco Dwarf Spheroidal Galaxy
• The Status of Multi-Dimensional Core-Collapse Supernova Models
• Complete element abundances of nine stars in the r-process galaxy Reticulum II
• Integrated Nucleosynthesis in Neutrino Driven Winds
• How many nucleosynthesis processes exist at low metallicity?
• New insights on Ba over-abundance in open clusters. Evidence for the intermediate neutron-capture process at play?
• Nine New Metal-Poor Stars on the Subgiant and Red Horizontal Branches with High Levels of r-process Enhancement
• Nucleosynthesis in magneto-rotational supernovae
• Chemical Inhomogeneities in the Milky Way Stellar Halo
• Abundances and kinematics of carbon-enhanced metal-poor stars in the Galactic halo*; A new classification scheme based on Sr and Ba
• New Detections of Arsenic, Selenium, and Other Heavy Elements in Two Metal-Poor Stars
• Horizons: Nuclear Astrophysics in the 2020s and Beyond
• Element abundance patterns in stars indicate fission of nuclei heavier than uranium
• Stellar abundances and presolar grains trace the nucleosynthetic origin of molybdenum and ruthenium
• The R-Process Alliance: Abundance Universality among Some Elements at and between the First and Second R-Process Peaks
• Observing the metal-poor solar neighbourhood: a comparison of galactic chemical evolution predictions
• Role of ($\alpha$,n) reactions under $r$-process conditions in neutrino-driven winds revisited
• Chemical Evolution of R-process Elements in Stars (CERES). I. Stellar parameters and chemical abundances from Na to Zr
• Enrichment of the Galactic disc with neutron capture elements: Sr
• Dark Lepton Superfluid in Proto-Neutron Stars
• Impact of nuclear matter properties on the nucleosynthesis and the kilonova from binary neutron star merger ejecta
• Chemical Evolution of R-process Elements in Stars (CERES). III. Chemical abundances of neutron capture elements from Ba to Eu
• Recent Progress in the Understanding of the r-Process
• Abundances in Metal-Poor Stars and Chemical Evolution of the Early Galaxy
• UVES analysis of red giants in the bulge globular cluster NGC 6522
• Beta decay studies of r-process nuclei at the National Superconducting Cyclotron Laboratory