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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Jose C. APONTE^1,2*, Hannah K. WOODWARD^2,3, Neyda M. ABREU⁴, Jamie E. ELSILA¹, and Jason P. DWORKIN¹
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13216 ]
¹Solar System Exploration Division, Code 691, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
²Department of Chemistry, Catholic University of America, Washington, DC 20064, USA
³Department of Chemistry, University of Reading, Reading RG6 6UA, UK
⁴Earth Science Program, Pennsylvania State University—Du Bois Campus, Du Bois, Pennsylvania 15801, USA
Published by arrangement with John Wiley & Sons

The water‐soluble organic compounds in carbonaceous chondrite meteorites constitute a record of the synthetic reactions occurring at the birth of the solar system and those taking place during parent body alteration and may have been important for the later origins and development of life on Earth. In this present work, we have developed a novel methodology for the simultaneous analysis of the molecular distribution, compound‐specific δ¹³C, and enantiomeric compositions of aliphatic monocarboxylic acids (MCA) extracted from the hot‐water extracts of 16 carbonaceous chondrites from CM, CR, CO, CV, and CK groups. We observed high concentrations of meteoritic MCAs, with total carbon weight percentages which in some cases approached those of carbonates and insoluble organic matter. Moreover, we found that the concentration of MCAs in CR chondrites is higher than in the other meteorite groups, with acetic acid exhibiting the highest concentration in all samples. The abundance of MCAs decreased with increasing molecular weight and with increasing aqueous and/or thermal alteration experienced by the meteorite sample. The δ¹³C isotopic values of MCAs ranged from −52 to +27‰, and aside from an inverse relationship between δ¹³C value and carbon straight‐chain length for C₃–C₆ MCAs in Murchison, the ¹³C‐isotopic values did not correlate with the number of carbon atoms per molecule. We also observed racemic compositions of 2‐methylbutanoic acid in CM and CR chondrites. We used this novel analytical protocol and collective data to shed new light on the prebiotic origins of chondritic MCAs.

Leonardo Krapp¹, Oliver Gressel^1,2, Pablo Benítez-Llambay¹, Turlough P. Downes³, Gopakumar Mohandas^1,2, and Martin E. Pessah¹
Astrophysical Journal 865, 105 Link to Article [DOI: 10.3847/1538-4357/aadcf0]
¹Niels Bohr International Academy, The Niels Bohr Institute, Blegdamsvej 17, DK-2100, Copenhagen Ø, Denmark
²Kavli Institute for Theoretical Physics, University of California, Santa Barbara 93106, USA
³Centre for Astrophysics & Relativity, School of Mathematical Sciences, Dublin City University (DCU), Ireland

Imaging of the dust continuum emitted from disks around nearby protostars reveals diverse substructure. In recent years, theoretical efforts have been intensified to investigate how far the intrinsic dynamics of protoplanetary disks (PPDs) can lead to such features. Turbulence in the realm of non-ideal magnetohydrodynamics (MHD) is one candidate for explaining the generation of zonal flows which can lead to local dust enhancements. Adopting a radially varying cylindrical disk model, and considering combinations of vertical and azimuthal initial net flux, we perform 3D non-ideal MHD simulations aimed at studying self-organization induced by the Hall effect in turbulent PPDs. To this end, new modules have been incorporated into the Nirvana-iii and FARGO3D MHD codes. We moreover include dust grains, treated in the fluid approximation, in order to study their evolution subject to the emerging zonal flows. In the regime of a dominant Hall effect, we robustly obtain large-scale organized concentrations in the vertical magnetic field that remain stable for hundreds of orbits. For disks with vertical initial net flux alone, we confirm the presence of zonal flows and vortices that introduce regions of super-Keplerian gas flow. Including a moderately strong net-azimuthal magnetic flux can significantly alter the dynamics, partially preventing the self-organization of zonal flows. For plasma beta-parameters smaller than 50, large-scale, near-axisymmetric structures develop in the vertical magnetic flux. In all cases, we demonstrate that the emerging features are capable of accumulating dust grains for a range of Stokes numbers.

¹Maria Rosa Scicchitano,^1,2,3Daniela Rubatto, ^1,2Jörg Hermann, ⁴Alik S.Majumdar, ⁵Andrew Putnis
Chemical Geology 499, 126-137 Link to Article [https://doi.org/10.1016/j.chemgeo.2018.09.020]
¹Research School of Earth Sciences, Australian National University, Canberra 2601, ACT, Australia
²Institute of Geological Sciences, University of Bern, 3012 Bern, Switzerland
³Institute of Earth Sciences, University of Lausanne, Geopolis, 1015 Lausanne, Switzerland
⁴Geosciences Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, Gujarat, India
⁵The Institute for Geoscience Research, Curtin University, Perth 6845, WA, Australia

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Sanemichi Z. Takahashi^1,2 and Takayuki Muto³
Astrophysical Journal 865, 102 Link to Article [DOI: 10.3847/1538-4357/aadda0]
¹Department of Applied Physics, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677, Japan
²National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
³Division of Liberal Arts, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677, Japan

Structure formation in young protoplanetary disks is investigated using a one-dimensional model including the formation and the evolution of disks. Recent observations with ALMA found that a ring–hole structure may be formed in young protoplanetary disks, even when the disk is embedded in the envelope. We present a one-dimensional model for the formation of a protoplanetary disk from a molecular cloud core and its subsequent long-term evolution within a single framework. Such long-term evolution has not been explored by numerical simulations due to the limitations of computational power. In our model, we calculate the time evolution of the surface density of the gas and dust with the wind mass loss and the radial drift of the dust in the disk. We find that the MHD disk wind is a viable mechanism for the formation of a ring–hole structure in young disks. We perform a parameter study of our model and derive conditions for the formation of ring–hole structures within 6 × 10⁵ yr after the start of the collapse of the molecular cloud core. The final outcome of the disk shows five types of morphology; this can be understood by comparing the timescales of the viscous diffusion, the mass loss by MHD disk wind, and the radial drift of the dust. We discuss the implication of the model for the WL 17 system, which is suspected to be an embedded, yet transitional, disk.

¹Yu.Shkuratov, ¹Ye.Surkov, ²M.Ivanov, ¹V.Korokhin, ¹V.Kaydash, ³G.Videen, ⁴C.Pieters, ¹D.Stankevich
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.11.002]
¹V.N. Karazin Kharkiv National University, 35 Sumska St, Kharkiv, 61022, Ukraine
²V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19, Kosygin st., 119991 Moscow, Russia
³Space Science Institute, 4750 Walnut St. Suite 205, Boulder CO 80301, USA
⁴Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA
Copyright Elsevier

We provide and test a method to obtain significant improvement of available Chandrayaan-1 M³ data. The advance is achieved using the Gaussian λ-convolution of spectra and Fourier filtration of images. The main result is imagery of the reflectance across different wavelengths as well as parameters of 1 μm and 2 μm absorption bands with unprecedented quality. This approach can be particularly useful for further investigations using M³ data, since it produces improved imagery of various lunar surface characteristics. We studied a region comprising a portion of the Aristarchus Plateau, Montes Agricola, and a small part of the mare surface in Ocean Procellarum to the north of Montes Agricola. We found that the lava flows in the area between the Aristarchus Plateau and Montes Agricola have a chemical/mineral composition different in comparison with mare areas to the northwest of the ridge Montes Agricola. We also identified distinct spectral properties of morphologically young craters located on the plateau and mare surface. A correlation diagram for positions of the minima of the 1 μm and 2 μm bands allows a cluster analysis of the region, and we map areas associated with a cluster corresponding to pyroclastic glasses. Relationships between geologic and spectral parameter maps were established.

¹Speelmanns, I.M., ¹Schmidt, M.W., ¹Liebske, C.
Geophysical Research Letters 45, 7434-7443 Link to Article [DOI: 10.1029/2018GL079130]
¹ETH Zurich, Department of Earth Sciences, Zurich ZH,, Switzerland

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Daiki Yamamoto¹, Minami Kuroda¹, Shogo Tachibana^1,2, Naoya Sakamoto³, and Hisayoshi Yurimoto^1,4
Astrophysical Journal 865, 98 Link to Article [DOI: 10.3847/1538-4357/aadcee]
¹Department of Natural History Sciences, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
²UTokyo Organization for Planetary Space Science, The University of Tokyo, Hongo, Tokyo 113-0033, Japan
³Isotopic Imaging Laboratory, Hokkaido University, Sapporo, 001-0021, Japan
⁴Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa, 252-210, Japan

Meteoritic evidence suggests that oxygen isotopic exchange between ¹⁶O-rich amorphous silicate dust and ¹⁶O-poor water vapor occurred in the early solar system. In this study, we experimentally investigated the kinetics of oxygen isotopic exchange between submicron-sized amorphous forsterite grains and water vapor at protoplanetary disk-like low pressures of water vapor. The isotopic exchange reaction rate is controlled either by diffusive isotopic exchange in the amorphous structure or by the supply of water molecules from the vapor phase. The diffusive oxygen isotopic exchange occurred with a rate constant D (m² s⁻¹) = (1.5 ± 1.0) × 10⁻¹⁹ exp[−(161.5 ± 14.1 (kJ mol⁻¹))R⁻¹(1/T−1/1200)] at temperatures below ~800–900 K, and the supply of water molecules from the vapor phase could determine the rate of oxygen isotopic exchange at higher temperatures in the protosolar disk. On the other hand, the oxygen isotopic exchange rate dramatically decreases if the crystallization of amorphous forsterite precedes the oxygen isotopic exchange reaction with amorphous forsterite. According to the kinetics for oxygen isotopic exchange in protoplanetary disks, original isotopic compositions of amorphous forsterite dust could be preserved only if the dust was kept at temperatures below 500–600 K in the early solar system. The ¹⁶O-poor signatures for the most pristine silicate dust observed in cometary materials implies that the cometary silicate dust experienced oxygen isotopic exchange with ¹⁶O-poor water vapor through thermal annealing at temperatures higher than 500–600 K prior to their accretion into comets in the solar system.