New Detections of Arsenic, Selenium, and Other Heavy Elements in Two Metal-Poor Stars

Abstract

We use the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope to obtain new high-quality spectra covering the 1900 to 2360 Angstrom 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 (std. dev. = 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 (std. dev. = 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 begins to dominate the quasi-equilibrium alpha-rich freezeout of the iron peak. <[CuII/CuI]> = +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.

arXiv commentAccepted for publication in the Astrophysical Journal. 13 pages, 10 figures

References in corpus (34)

• Galactic Evolution of Sr, Y, Zr: A Multiplicity of Nucleosynthetic Processes
• Neutrino-induced nucleosynthesis of A>64 nuclei: The nu p-process
• The Extremely Metal-Poor, Neutron-Capture-Rich Star CS 22892-052: A Comprehensive Abundance Analysis
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• The extreme r-element rich, iron-poor halo giant CS31082-001: Implications for the r-process site(s) and radioactive cosmochronology
• The Chemical Composition and Age of the Metal-Poor Halo Star BD +17^\circ 3248
• The Abundances of Neutron Capture Species in the Very Metal-Poor Globular Cluster M15: An Uniform Analysis of RGB and RHB Stars
• The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models
• Nucleosynthesis in Early Supernova Winds II: The Role of Neutrinos
• Near-UV Observations of HD221170: New Insights into the Nature of r-Process-Rich Stars
• Charged-Particle and Neutron-Capture Processes in the High-Entropy Wind of Core-Collapse Supernovae
• New Rare Earth Element Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars
• Spectroscopic Studies of Very Metal-Poor Stars with the Subaru High Dispersion Spectrograph. III. Light Neutron-Capture Elements
• The Ubiquity of the Rapid Neutron-Capture Process
• Nucleosynthesis in the Early Galaxy
• Detection of Elements at All Three r-process Peaks in the Metal-Poor Star HD 160617
• Silver and palladium help unveil the nature of a second r-process
• New Hubble Space Telescope Observations of Heavy Elements in Four Metal-Poor Stars
• Improved Ti II log(gf) Values and Abundance Determinations in the Photospheres of the Metal-Poor Star HD 84937
• HST Observations of Heavy Elements in Metal-Poor Galactic Halo Stars
• The End of Nucleosynthesis: Production of Lead and Thorium in the Early Galaxy
• Improved Ni I log(gf) Values and Abundance Determinations in the Photospheres of the Sun and Metal-poor Star HD 84937
• First stars XVI. STIS/HST abundances of heavy-elements in the uranium-rich star CS 31082-001
• Half-lives and branchings for β-delayed neutron emission for neutron-rich Co-Cu isotopes in the r-process
• Abundances of Sr, Y, and Zr in Metal-Poor Stars and Implications for Chemical Evolution in the Early Galaxy
• The r-process in the early Galaxy
• Chemical Analysis of the Ninth Magnitude Carbon-Enhanced Metal-Poor Star BD+44 493
• Mass measurements beyond the major r-process waiting point 80Zn
• New Abundance Determinations of Cadmium, Lutetium, and Osmium in the r-process Enriched Star BD+173248
• Non-LTE effects on the lead and thorium abundance determinations for cool stars
• Detection of the Second r-process Peak Element Tellurium in Metal-Poor Stars
• Germanium, Arsenic, and Selenium Abundances in Metal-Poor Stars
• Hubble Space Telescope Near-Ultraviolet Spectroscopy of the Bright CEMP-no Star BD+44 493
• The Extreme Overabundance of Molybdenum in Two Metal-Poor Stars

Cited by in corpus (42)

• Origin of the Heaviest Elements: the Rapid Neutron-Capture Process
• Neutron Star Mergers and Nucleosynthesis of Heavy Elements
• NuGrid stellar data set I. Stellar yields from H to Bi for stars with metallicities Z = 0.02 and Z = 0.01
• r-Process Nucleosynthesis: Connecting Rare-Isotope Beam Facilities with the Cosmos
• JINAbase: A database for chemical abundances of metal-poor stars
• Radioactive decay products in neutron star merger ejecta: heating efficiency and $\gamma$-ray emission
• The R-Process Alliance: A Comprehensive Abundance Analysis of HD 222925, a Metal-Poor Star with an Extreme R-Process Enhancement of [Eu/H] = -0.14
• The Diverse Origins of Neutron-Capture Elements in the Metal-Poor Star HD 94028: Possible Detection of Products of i-process Nucleosynthesis
• The Influence of Neutrinos on r-Process Nucleosynthesis in the Ejecta of Black Hole-Neutron Star Mergers
• Nine New Metal-Poor Stars on the Subgiant and Red Horizontal Branches with High Levels of r-process Enhancement
• Detection of Neutral Phosphorus in the Near Ultraviolet Spectra of Late-Type Stars
• Horizons: Nuclear Astrophysics in the 2020s and Beyond
• Hubble Space Telescope Near-Ultraviolet Spectroscopy of Bright CEMP-s Stars
• Element abundance patterns in stars indicate fission of nuclei heavier than uranium
• Galactic evolution of Copper in the light of NLTE computations
• Spectroscopic Validation of Low-Metallicity Stars from RAVE
• The Abundances of Light Neutron-Capture Elements in Planetary Nebulae III. The Impact of New Atomic Data on Nebular Selenium and Krypton Abundance Determinations
• The R-Process Alliance: Spectroscopic Follow-up of Low-Metallicity Star Candidates from the Best & Brightest Survey
• A New Test of Copper and Zinc Abundances in Late-Type Stars Using Ultraviolet Cu II and Zn II Lines
• Non-LTE analysis of copper abundances for the two distinct halo populations in the solar neighborhood
• Non-LTE analysis of neutral copper in the late-type metal-poor stars
• The R-Process Alliance: Abundance Universality among Some Elements at and between the First and Second R-Process Peaks
• Neutron-Capture elements in planetary nebulae: first detections of near-Infrared [Te III] and [Br V] emission lines
• NLTE analysis of copper lines in different stellar populations
• Detailed Iron-Peak Element Abundances in Three Very Metal-Poor Stars
• Trans-iron Ge, As, Se, and heavier elements in the dwarf metal-poor stars, HD~19445, HD~84937, HD~94028, HD~140283, and HD~160617
• Abundances and Depletions of Neutron-Capture Elements in the Interstellar Medium
• Chemical Evolution of Ytterbium in the Galactic Disk
• Detection of Al II in the Ultraviolet Spectra of Metal-Poor Stars: An Empirical LTE Test of NLTE Aluminum Abundance Calculations
• The impact of (n,$\gamma$) reaction rate uncertainties on the predicted abundances of i-process elements with $32\le Z\le 48$ in the metal-poor star HD94028
• Relativistic coupled-cluster theory analysis of energies, hyperfine structure constants, and dipole polarizabilities of Cd${}^{+}$
• Detection of Pb II in the Ultraviolet Spectra of Three Metal-Poor Stars
• Chemical Evolution of R-process Elements in Stars (CERES): IV. An observational run-up of the third r-process peak with Hf, Os, Ir, and Pt
• Revisiting inelastic Cu+H collisions and the non-LTE Galactic evolution of copper
• Nucleosynthesis signatures of neutrino-driven winds from proto-neutron stars: a perspective from chemical evolution models
• Deep SDSS Optical Spectroscopy of Distant Halo Stars. III. Chemical analysis of extremely metal-poor stars
• Single photoionization of the Zn II ion in the photon energy range 17.5 to 90.0 eV: experiment and theory
• Explosive Nucleosynthesis: What we learned and what we still do not understand
• Abundances of disk and bulge giants from high-resolution optical spectra V. Molybdenum -- the p-process element
• Revisiting the iron abundance in the hyper iron-poor star HE 1327-2326 with UV COS/$HST$ data
• The R-Process Alliance: Hunting for gold in the near-UV spectrum of 2MASS J05383296-5904280
• The R-Process Alliance: A Nearly Complete R-Process Abundance Template Derived from Ultraviolet Spectroscopy of the R-Process-Enhanced Metal-Poor Star HD 222925