David V. BEKAERT^1*, Yves MARROCCHI¹, Alex MESHIK², Laurent REMUSAT³, and Bernard MARTY¹
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13213]
¹Centre de Recherches Petrographiques et Geochimiques, CRPG-CNRS, Universite de Lorraine, UMR 7358, 15 rue NotreDame des Pauvres, BP 20, 54501 Vandoeuvre-les-Nancy, France
²Department of Physics, Washington University, 1 Brookings Drive, Saint Louis, Missouri 63130, USA
³Institut de Mineralogie, de Physique des Materiaux et de Cosmochimie (IMPMC), UMR CNRS 7590 – Sorbonne, Universites -UPMC – IRD – Museum National d’Histoire Naturelle, 57 rue Cuvier, Case 52, 75231 Paris Cedex 5, France
Published by arrangement with John Wiley & Sons

The Paris carbonaceous chondrite represents the most pristine carbonaceous chondrite, providing a unique opportunity to investigate the composition of early solar system materials prior to the onset of significant aqueous alteration. A dual origin (namely from the inner and outer solar system) has been demonstrated for water in the Paris meteorite parent body (Piani et al. 2018). Here, we aim to evaluate the contribution of outer solar system (cometary‐like) water ice to the inner solar system water ice using Xe isotopes. We report Ar, Kr, and high‐precision Xe isotopic measurements within bulk CM 2.9 and CM 2.7 fragments, as well as Ne, Ar, Kr, and Xe isotope compositions of the insoluble organic matter (IOM). Noble gas signatures are similar to chondritic phase Q with no evidence for a cometary‐like Xe component. Small excesses in the heavy Xe isotopes relative to phase Q within bulk samples are attributed to contributions from presolar materials. CM 2.7 fragments have lower Ar/Xe relative to more pristine CM 2.9 fragments, with no systematic difference in Xe contents. We conclude that Kr and Xe were little affected by aqueous alteration, in agreement with (1) minor degrees of alteration and (2) no significant differences in the chemical signature of organic matter in CM 2.7 and CM 2.9 areas (Vinogradoff et al. 2017). Xenon contents in the IOM are larger than previously published data of Xe in chondritic IOM, in line with the Xe component in Paris being pristine and preserved from Xe loss during aqueous alteration/thermal metamorphism.

J. Bliss¹, A. Arcones^1,2, and Y.-Z. Qian^3,4
Astrophysical Journal 866, 105 Link to Article [DOI: 10.3847/1538-4357/aade8d]
¹Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstr. 2, Darmstadt D-64289, Germany
²GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstr. 1, Darmstadt D-64291, Germany
³School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
⁴Tsung-Dao Lee Institute, Shanghai 200240, People’s Republic of China

The origin of the so-called p-isotopes and in the solar system remains a mystery, as several astrophysical scenarios fail to account for them. In addition, data on presolar silicon carbide grains of type X (SiC X) exhibit peculiar Mo patterns, especially for . We examine the production of Mo and Ru isotopes in neutrino-driven winds associated with core-collapse supernovae (CCSNe) over a wide range of conditions. We find that proton-rich winds can make dominant contributions to the solar abundance of and significant contributions to those of ⁹⁶Ru, ⁹²Mo, and ⁹⁴Mo. In contrast, neutron-rich winds make negligible contributions to the solar abundances of ^92,94Mo and cannot produce ^96,98Ru, whereas the early ejecta of CCSNe can make dominant contributions to the solar abundance of ⁹²Mo. Furthermore, we show that some neutron-rich winds can account for the peculiar Mo patterns in SiC X grains. Our results can be generalized if conditions similar to those studied here are also obtained for other types of ejecta in either CCSNe or neutron star mergers.

Ian U. Roederer^1,2, Charli M. Sakari³, Vinicius M. Placco^2,4, Timothy C. Beers^2,4, Rana Ezzeddine^2,5, Anna Frebel^2,5, and Terese T. Hansen⁶
Astrophysical Journal 865, 129 Link to Article [DOI: 10.3847/1538-4357/aadd92]
¹Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109, USA
²Joint Institute for Nuclear Astrophysics—Center for the Evolution of the Elements (JINA-CEE), USA
³Department of Astronomy, University of Washington, Seattle, WA 98195-1580, USA
⁴Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA
⁵Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
⁶Carnegie Observatories, Pasadena, CA 91101, USA

We present a detailed abundance analysis of the bright (V = 9.02), metal-poor ([Fe/H] = −1.47 ± 0.08) field red horizontal-branch star HD 222925, which was observed as part of an ongoing survey by the R-Process Alliance. We calculate stellar parameters and derive abundances for 46 elements based on 901 lines examined in a high-resolution optical spectrum obtained using the Magellan Inamori Kyocera Echelle spectrograph. We detect 28 elements with 38 ≤ Z ≤ 90; their abundance pattern is a close match to the solar r-process component. The distinguishing characteristic of HD 222925 is an extreme enhancement of r-process elements ([Eu/Fe] = +1.33 ± 0.08, [Ba/Eu] = −0.78 ± 0.10) in a moderately metal-poor star, so the abundance of r-process elements is the highest ([Eu/H] = −0.14 ± 0.09) in any known r-process-enhanced star. The abundance ratios among lighter (Z ≤ 30) elements are typical for metal-poor stars, indicating that production of these elements was dominated by normal Type II supernovae, with no discernible contributions from Type Ia supernovae or asymptotic giant branch stars. The chemical and kinematic properties of HD 222925 suggest it formed in a low-mass dwarf galaxy, which was enriched by a high-yield r-process event before being disrupted by interaction with the Milky Way.

¹Senesi, G.S., ²Manzari, P., ³Consiglio, A., ¹De Pascale, O.
Journal of Analytical Atomic Spectroscopy 33, 1664-1675 Link to Article [DOI: 10.1039/c8ja00224j]
¹CNR-Istituto di Nanotecnologia (NANOTEC) PLasMI Lab, Via Amendola 122/D, Bari, 70126, Italy
²Istituto Nazionale di Astrofisica-Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS), Via Fosso del Cavaliere 100, Roma, Italy
³CNR-Istituto di Tecnologie Biomediche (ITB), Via Amendola 122/D, Bari, 70126, Italy

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