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Collapsars As a Major Source of R-Process Elements
Collapsars as a major source of r-process elements Daniel M. Siegel1;2;3;4;5, Jennifer Barnes1;2;5 & Brian D. Metzger1;2 1Department of Physics, Columbia University, New York, NY, USA 2Columbia Astrophysics Laboratory, Columbia University, New York, NY, USA 3Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada 4Department of Physics, University of Guelph, Guelph, Ontario, Canada 5NASA Einstein Fellow The production of elements by rapid neutron capture (r-process) in neutron-star mergers is expected theoretically and is supported by multimessenger observations1–3 of gravitational- wave event GW170817: this production route is in principle sufficient to account for most of the r-process elements in the Universe4. Analysis of the kilonova that accompanied GW170817 identified5, 6 delayed outflows from a remnant accretion disk formed around the newly born black hole7–10 as the dominant source of heavy r-process material from that event9, 11. Sim- ilar accretion disks are expected to form in collapsars (the supernova-triggering collapse of rapidly rotating massive stars), which have previously been speculated to produce r-process elements12, 13. Recent observations of stars rich in such elements in the dwarf galaxy Retic- arXiv:1810.00098v2 [astro-ph.HE] 14 Aug 2020 ulum II14, as well as the Galactic chemical enrichment of europium relative to iron over longer timescales15, 16, are more consistent with rare supernovae acting at low stellar metal- licities than with neutron-star mergers. Here we report simulations that show that collapsar accretion disks yield sufficient r-process elements to explain observed abundances in the Uni- 1 verse. Although these supernovae are rarer than neutron- star mergers, the larger amount of material ejected per event compensates for the lower rate of occurrence. -
R-Process Elements from Magnetorotational Hypernovae
r-Process elements from magnetorotational hypernovae D. Yong1,2*, C. Kobayashi3,2, G. S. Da Costa1,2, M. S. Bessell1, A. Chiti4, A. Frebel4, K. Lind5, A. D. Mackey1,2, T. Nordlander1,2, M. Asplund6, A. R. Casey7,2, A. F. Marino8, S. J. Murphy9,1 & B. P. Schmidt1 1Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia 2ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia 3Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield, AL10 9AB, UK 4Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 5Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden 6Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany 7School of Physics and Astronomy, Monash University, VIC 3800, Australia 8Istituto NaZionale di Astrofisica - Osservatorio Astronomico di Arcetri, Largo Enrico Fermi, 5, 50125, Firenze, Italy 9School of Science, The University of New South Wales, Canberra, ACT 2600, Australia Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1–3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4–6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7–13. -
Concrete Analysis by Neutron-Capture Gamma Rays Using Californium 252
CONCRETE ANALYSIS BY NEUTRON-CAPTURE GAMMA RAYS USING CALIFORNIUM 252 Dick Duffey, College of Engineering, University of Maryland; Peter F. Wiggins, Naval Systems Engineering Department, U.S. Naval Academy; Frank E. Senftle, U.S. Geological Survey; and A. A. El Kady, United Arab Republic Atomic Energy Establishment, Cairo The feasibility of analyzing concrete and cement by a measurement of the neutron-capture or prompt gamma rays was investigated; a 100-ug californium-252 source was used to supply the neutrons. A lithium drifted germanium crystal detected the capture gamma rays emitted. The capture gamma rays from cement, sand, and 3 coarse aggregates-quartzite gravel, limestone, and diabase--:were studied. Concrete blocks made from these materials were then tested. The capture gamma ray response of the calcium, silicon, and iron in the concrete blocks was in accord with the elements identified in the mix materials. The principal spectral lines used were the 6.42 MeV line of calcium, the 4.93 MeV line of silicon, and the doublet of iron at about 7 .64 MeV. The aluminum line at 7. 72 MeV was ob served in some cases but at a lower intensity with the limited electronic equipment available. This nuclear spectroscopic technique offers a possi ble method of determining the components of sizable concrete samples in a nondestructive, in situ manner. In addition, the neutron-capture gamma ray technique might find application in control of the concrete and cement processes and furnish needed information on production operations and inventories. • FROM THE point of view of the geochemical analyst, concrete may be considered as rock relocated and reformed at the convenience of the engineer. -
Minicourses in Astrophysics, Modular Approach, Vol
DOCUMENT RESUME ED 161 706 SE n325 160 ° TITLE Minicourses in Astrophysics, Modular Approach, Vol.. II. INSTITUTION Illinois Univ., Chicago. SPONS AGENCY National Science Foundation, Washington, D. BUREAU NO SED-75-21297 PUB DATE 77 NOTE 134.,; For related document,. see SE 025 159; Contains occasional blurred,-dark print EDRS PRICE MF-$0.83 HC- $7..35 Plus Postage. DESCRIPTORS *Astronomy; *Curriculum Guides; Evolution; Graduate 1:-Uldy; *Higher Edhcation; *InstructionalMaterials; Light; Mathematics; Nuclear Physics; *Physics; Radiation; Relativity: Science Education;. *Short Courses; Space SCiences IDENTIFIERS *Astrophysics , , ABSTRACT . This is the seccA of a two-volume minicourse in astrophysics. It contains chaptez:il on the followingtopics: stellar nuclear energy sources and nucleosynthesis; stellarevolution; stellar structure and its determinatioli;.and pulsars.Each chapter gives much technical discussion, mathematical, treatment;diagrams, and examples. References are-included with each chapter.,(BB) e. **************************************t****************************- Reproductions supplied by EDRS arethe best-that can be made * * . from the original document. _ * .**************************4******************************************** A U S DEPARTMENT OF HEALTH. EDUCATION &WELFARE NATIONAL INSTITUTE OF EDUCATION THIS DOCUMENT AS BEEN REPRO' C'')r.EC! EXACTLY AS RECEIVED FROM THE PERSON OR ORGANIZATION'ORIGIkl A TINC.IT POINTS OF VIEW OR OPINIONS aft STATED DO NOT NECESSARILY REPRE SENT OFFICIAL NATIONAL INSTITUTE Of EDUCATION POSITION OR POLICY s. MINICOURSES IN ASTROPHYSICS MODULAR APPROACH , VOL. II- FA DEVELOPED'AT THE hlIVERSITY OF ILLINOIS AT CHICAGO 1977 I SUPPORTED BY NATIONAL SCIENCE FOUNDATION DIRECTOR: S. SUNDARAM 'ASSOCIATETIRECTOR1 J. BURNS _DEPARTMENT OF PHYSICS. DEPARTMENT OF PHYSICS AND SPACE UNIVERSITY OF ILLINOIS SCIENCES CHICAGO, ILLINOIS 60680 FLORIDA INSTITUTE OF TECHNOLOGY MELBOURNE, FLORIDA 32901 0 0 4, STELLAR NUCLEAR ENERGY SOURCES and NUCLEGSYNTHESIS 'I. -
Nuclear Astrophysics: the Unfinished Quest for the Origin of the Elements
Nuclear astrophysics: the unfinished quest for the origin of the elements Jordi Jos´e Departament de F´ısica i Enginyeria Nuclear, EUETIB, Universitat Polit`ecnica de Catalunya, E-08036 Barcelona, Spain; Institut d’Estudis Espacials de Catalunya, E-08034 Barcelona, Spain E-mail: [email protected] Christian Iliadis Department of Physics & Astronomy, University of North Carolina, Chapel Hill, North Carolina, 27599, USA; Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA E-mail: [email protected] Abstract. Half a century has passed since the foundation of nuclear astrophysics. Since then, this discipline has reached its maturity. Today, nuclear astrophysics constitutes a multidisciplinary crucible of knowledge that combines the achievements in theoretical astrophysics, observational astronomy, cosmochemistry and nuclear physics. New tools and developments have revolutionized our understanding of the origin of the elements: supercomputers have provided astrophysicists with the required computational capabilities to study the evolution of stars in a multidimensional framework; the emergence of high-energy astrophysics with space-borne observatories has opened new windows to observe the Universe, from a novel panchromatic perspective; cosmochemists have isolated tiny pieces of stardust embedded in primitive meteorites, giving clues on the processes operating in stars as well as on the way matter condenses to form solids; and nuclear physicists have measured reactions near stellar energies, through the combined efforts using stable and radioactive ion beam facilities. This review provides comprehensive insight into the nuclear history of the Universe arXiv:1107.2234v1 [astro-ph.SR] 12 Jul 2011 and related topics: starting from the Big Bang, when the ashes from the primordial explosion were transformed to hydrogen, helium, and few trace elements, to the rich variety of nucleosynthesis mechanisms and sites in the Universe. -
Iron Isotope Cosmochemistry Kun Wang Washington University in St
Washington University in St. Louis Washington University Open Scholarship All Theses and Dissertations (ETDs) 12-2-2013 Iron Isotope Cosmochemistry Kun Wang Washington University in St. Louis Follow this and additional works at: https://openscholarship.wustl.edu/etd Part of the Earth Sciences Commons Recommended Citation Wang, Kun, "Iron Isotope Cosmochemistry" (2013). All Theses and Dissertations (ETDs). 1189. https://openscholarship.wustl.edu/etd/1189 This Dissertation is brought to you for free and open access by Washington University Open Scholarship. It has been accepted for inclusion in All Theses and Dissertations (ETDs) by an authorized administrator of Washington University Open Scholarship. For more information, please contact [email protected]. WASHINGTON UNIVERSITY IN ST. LOUIS Department of Earth and Planetary Sciences Dissertation Examination Committee: Frédéric Moynier, Chair Thomas J. Bernatowicz Robert E. Criss Bruce Fegley, Jr. Christine Floss Bradley L. Jolliff Iron Isotope Cosmochemistry by Kun Wang A dissertation presented to the Graduate School of Arts and Sciences of Washington University in partial fulfillment of the requirements for the degree of Doctor of Philosophy December 2013 St. Louis, Missouri Copyright © 2013, Kun Wang All rights reserved. Table of Contents LIST OF FIGURES ....................................................................................................................... vi LIST OF TABLES ........................................................................................................................ -
Announcements
Announcements • Next Session – Stellar evolution • Low-mass stars • Binaries • High-mass stars – Supernovae – Synthesis of the elements • Note: Thursday Nov 11 is a campus holiday Red Giant 8 100Ro 10 years L 10 3Ro, 10 years Temperature Red Giant Hydrogen fusion shell Contracting helium core Electron Degeneracy • Pauli Exclusion Principle says that you can only have two electrons per unit 6-D phase- space volume in a gas. DxDyDzDpxDpyDpz † Red Giants • RG Helium core is support against gravity by electron degeneracy • Electron-degenerate gases do not expand with increasing temperature (no thermostat) • As the Temperature gets to 100 x 106K the “triple-alpha” process (Helium fusion to Carbon) can happen. Helium fusion/flash Helium fusion requires two steps: He4 + He4 -> Be8 Be8 + He4 -> C12 The Berylium falls apart in 10-6 seconds so you need not only high enough T to overcome the electric forces, you also need very high density. Helium Flash • The Temp and Density get high enough for the triple-alpha reaction as a star approaches the tip of the RGB. • Because the core is supported by electron degeneracy (with no temperature dependence) when the triple-alpha starts, there is no corresponding expansion of the core. So the temperature skyrockets and the fusion rate grows tremendously in the `helium flash’. Helium Flash • The big increase in the core temperature adds momentum phase space and within a couple of hours of the onset of the helium flash, the electrons gas is no longer degenerate and the core settles down into `normal’ helium fusion. • There is little outward sign of the helium flash, but the rearrangment of the core stops the trip up the RGB and the star settles onto the horizontal branch. -
Low-Energy Nuclear Physics Part 2: Low-Energy Nuclear Physics
BNL-113453-2017-JA White paper on nuclear astrophysics and low-energy nuclear physics Part 2: Low-energy nuclear physics Mark A. Riley, Charlotte Elster, Joe Carlson, Michael P. Carpenter, Richard Casten, Paul Fallon, Alexandra Gade, Carl Gross, Gaute Hagen, Anna C. Hayes, Douglas W. Higinbotham, Calvin R. Howell, Charles J. Horowitz, Kate L. Jones, Filip G. Kondev, Suzanne Lapi, Augusto Macchiavelli, Elizabeth A. McCutchen, Joe Natowitz, Witold Nazarewicz, Thomas Papenbrock, Sanjay Reddy, Martin J. Savage, Guy Savard, Bradley M. Sherrill, Lee G. Sobotka, Mark A. Stoyer, M. Betty Tsang, Kai Vetter, Ingo Wiedenhoever, Alan H. Wuosmaa, Sherry Yennello Submitted to Progress in Particle and Nuclear Physics January 13, 2017 National Nuclear Data Center Brookhaven National Laboratory U.S. Department of Energy USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26) Notice: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No.DE-SC0012704 with the U.S. Department of Energy. The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or any third party’s use or the results of such use of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. -
Stellar Evolution
AccessScience from McGraw-Hill Education Page 1 of 19 www.accessscience.com Stellar evolution Contributed by: James B. Kaler Publication year: 2014 The large-scale, systematic, and irreversible changes over time of the structure and composition of a star. Types of stars Dozens of different types of stars populate the Milky Way Galaxy. The most common are main-sequence dwarfs like the Sun that fuse hydrogen into helium within their cores (the core of the Sun occupies about half its mass). Dwarfs run the full gamut of stellar masses, from perhaps as much as 200 solar masses (200 M,⊙) down to the minimum of 0.075 solar mass (beneath which the full proton-proton chain does not operate). They occupy the spectral sequence from class O (maximum effective temperature nearly 50,000 K or 90,000◦F, maximum luminosity 5 × 10,6 solar), through classes B, A, F, G, K, and M, to the new class L (2400 K or 3860◦F and under, typical luminosity below 10,−4 solar). Within the main sequence, they break into two broad groups, those under 1.3 solar masses (class F5), whose luminosities derive from the proton-proton chain, and higher-mass stars that are supported principally by the carbon cycle. Below the end of the main sequence (masses less than 0.075 M,⊙) lie the brown dwarfs that occupy half of class L and all of class T (the latter under 1400 K or 2060◦F). These shine both from gravitational energy and from fusion of their natural deuterium. Their low-mass limit is unknown. -
Stellar Evolution: Evolution Off the Main Sequence
Evolution of a Low-Mass Star Stellar Evolution: (< 8 M , focus on 1 M case) Evolution off the Main Sequence sun sun - All H converted to He in core. - Core too cool for He burning. Contracts. Main Sequence Lifetimes Heats up. Most massive (O and B stars): millions of years - H burns in shell around core: "H-shell burning phase". Stars like the Sun (G stars): billions of years - Tremendous energy produced. Star must Low mass stars (K and M stars): a trillion years! expand. While on Main Sequence, stellar core has H -> He fusion, by p-p - Star now a "Red Giant". Diameter ~ 1 AU! chain in stars like Sun or less massive. In more massive stars, 9 Red Giant “CNO cycle” becomes more important. - Phase lasts ~ 10 years for 1 MSun star. - Example: Arcturus Red Giant Star on H-R Diagram Eventually: Core Helium Fusion - Core shrinks and heats up to 108 K, helium can now burn into carbon. "Triple-alpha process" 4He + 4He -> 8Be + energy 8Be + 4He -> 12C + energy - First occurs in a runaway process: "the helium flash". Energy from fusion goes into re-expanding and cooling the core. Takes only a few seconds! This slows fusion, so star gets dimmer again. - Then stable He -> C burning. Still have H -> He shell burning surrounding it. - Now star on "Horizontal Branch" of H-R diagram. Lasts ~108 years for 1 MSun star. More massive less massive Helium Runs out in Core Horizontal branch star structure -All He -> C. Not hot enough -for C fusion. - Core shrinks and heats up. -
Lecture 7: "Basics of Star Formation and Stellar Nucleosynthesis" Outline
Lecture 7: "Basics of Star Formation and Stellar Nucleosynthesis" Outline 1. Formation of elements in stars 2. Injection of new elements into ISM 3. Phases of star-formation 4. Evolution of stars Mark Whittle University of Virginia Life Cycle of Matter in Milky Way Molecular clouds New clouds with gravitationally collapse heavier composition to form stellar clusters of stars are formed Molecular cloud Stars synthesize Most massive stars evolve He, C, Si, Fe via quickly and die as supernovae – nucleosynthesis heavier elements are injected in space Solar abundances • Observation of atomic absorption lines in the solar spectrum • For some (heavy) elements meteoritic data are used Solar abundance pattern: • Regularities reflect nuclear properties • Several different processes • Mixture of material from many, many stars 5 SolarNucleosynthesis abundances: key facts • Solar• Decreaseabundance in abundance pattern: with atomic number: - Large negative anomaly at Be, B, Li • Regularities reflect nuclear properties - Moderate positive anomaly around Fe • Several different processes 6 - Sawtooth pattern from odd-even effect • Mixture of material from many, many stars Origin of elements • The Big Bang: H, D, 3,4He, Li • All other nuclei were synthesized in stars • Stellar nucleosynthesis ⇔ 3 key processes: - Nuclear fusion: PP cycles, CNO bi-cycle, He burning, C burning, O burning, Si burning ⇒ till 40Ca - Photodisintegration rearrangement: Intense gamma-ray radiation drives nuclear rearrangement ⇒ 56Fe - Most nuclei heavier than 56Fe are due to neutron -
Oxygen-Burning Process
Oxygen-burning process The oxygen-burning process is a set of nuclear fusion reactions that take place in massive stars that have used up the lighter elements in their cores. Oxygen-burning is preceded by the neon-burning process and succeeded by the silicon-burning process. As the neon-burning process ends, the core of the star contracts and heats until it reaches the ignition temperature for oxygen burning. Oxygen burning reactions are similar to those of carbon burning; however, they must occur at higher temperatures and densities due to the larger Coulomb barrier of oxygen. Oxygen in the core ignites in the temperature range of (1.5–2.6)×109 K[1] and in the density range of (2.6–6.7)×109g/cm3.[2] The principal reactions are given below,[3][4] where the branching ratios assume that the deuteron channel is open (at high temperatures):[3] 16 + 16 → 28 + 4 + 9.593 MeV (34%) 8O 8O 14Si 2He → 31 + 1 + 7.676 MeV (56%) 15P 1H → 31 + + 1.459 MeV (5%) 16S n → 30 + 1 + 0.381 MeV 14Si 2 1H → 30 + 2 - 2.409 MeV (5%) 15P 1D Alternatively: → 32 + + 16.539 MeV 16S γ → 24 + 4 - 0.393 MeV 12Mg 2 2He [5][6][7][8][9] 9 −12 33 [3][5] Near 2×10 K, the oxygen burning reaction rate is approximately 2.8×10 (T9/2) , where T9 is the temperature in billions of Kelvin. Overall, the major products of the oxygen-burning process are [3] 28Si, 32,33,34S, 35,37Cl, 36,38Ar, 39,41K, and 40,42Ca.