B. S. Meyer

University of Chicago, Chicago, Illinois, United States

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Publications (74)79.79 Total impact

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    T. Yu, B. S. Meyer, D. D. Clayton
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    ABSTRACT: We here present calculations of dust condensation in core-collapse (Type II) and thermonuclear (Type Ia) supernovae, to understand the production of large dust grains in Type II supernovae and small dust grains in thermonuclear supernovae.
    Meteoritics and Planetary Science Supplement. 09/2013;
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    ABSTRACT: A common model of the explosion mechanism of Type Ia supernovae is based on a delayed detonation of a white dwarf. A variety of models differ primarily in the method by which the deflagration leads to a detonation. A common feature of the models, however, is that all of them involve the propagation of the detonation through a white dwarf that is either expanding or contracting, where the stellar internal velocity profile depends on both time and space. In this work, we investigate the effects of the pre-detonation stellar internal velocity profile and the post-detonation velocity of expansion on the production of alpha-particle nuclei, including Ni56, which are the primary nuclei produced by the detonation wave. We perform one-dimensional hydrodynamic simulations of the explosion phase of the white dwarf for center and off-center detonations with five different stellar velocity profiles at the onset of the detonation. We observe two distinct post-detonation expansion phases: rarefaction and bulk expansion. Almost all the burning to Ni56 occurs only in the rarefaction phase, and its expansion time scale is influenced by pre-existing flow structure in the star, in particular by the pre-detonation stellar velocity profile. We find that the mass fractions of the alpha-particle nuclei, including Ni56, are tight functions of the empirical physical parameter rho_up/v_down, where rho_up is the mass density immediately upstream of the detonation wave front and v_down is the velocity of the flow immediately downstream of the detonation wave front. We also find that v_down depends on the pre-detonation flow velocity. We conclude that the properties of the pre-existing flow, in particular the internal stellar velocity profile, influence the final isotopic composition of burned matter produced by the detonation.
    The Astrophysical Journal 06/2013; 771(1). · 6.73 Impact Factor
  • B. S. Meyer, M. J. Bojazi
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    ABSTRACT: We explore the sensitivity of helium burning production nitrogen-15 to supernova energies and reaction rates and the importance for low-density graphite grains.
    03/2013;
  • B. S. Meyer, M. J. Bojazi
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    ABSTRACT: Production of nitrogen-15 in explosive helium burning occurs by sequences of alpha and neutron capture reactions. Shocks stronger than in current supernova models increase the rates for these reactions and may help explain the N isotopes in presolar-grain SiC-X grains.
    03/2011;
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    ABSTRACT: We have studied more than 2000 presolar silicon carbide (SiC) grains from the Murchison CM2 chondrite in the size range 0.2-0.5 {mu}m for C- and Si-isotopic compositions. In a subset of these grains, we also measured N-, Mg-Al-, S-, and Ca-Ti-isotopic compositions as well as trace element concentrations. The overall picture emerging from the isotope data is quite comparable with that of larger grains, except for the abundances of grains from Type II supernovae (SNeII) and low-metallicity asymptotic giant branch (AGB) stars. Especially, the latter are much more abundant among submicrometer-sized grains than among micrometer-sized grains. This implies that SiC grains from lower-than-solar-metallicity AGB stars are on average smaller than those from solar metallicity AGB stars which provided the majority of presolar SiC grains. We identified five grains with large enrichments in {sup 29}Si (up to 3.5x solar) and {sup 30}Si (up to 3.9x solar in three of these grains). These grains are most likely from SNeII. The isotopically light S ({sup 32}S/{sup 34}S of 2x solar) together with the heavy Si in one of these grains suggests that molecule formation precedes macroscopic mixing and dust formation in SNII ejecta. This adds to the complexity of SN mixing calculations and should be considered in future studies. In total, about 2% of the presolar SiC grains in the size range 0.2-0.5 {mu}m appear to come from SNeII. This is about a factor of 2 higher than for micrometer-sized grains and suggests that SNeII, on average, produce smaller SiC grains than solar metallicity AGB stars. The high {sup 29}Si/{sup 30}Si ratio in one of the SN grains suggests that current SN models underestimate the {sup 29}Si production in the C- and Ne-burning regions by about a factor of 2. It is shown that with this adjustment the solar {sup 29}Si/{sup 28}Si ratio can be well reproduced in Galactic chemical evolution models and that a merger of our Galaxy with a low-metallicity satellite some 1.5 Gyr before solar system formation could account for the slope 1.3 of the Si mainstream line.
    The Astrophysical Journal 08/2010; · 6.73 Impact Factor
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    ABSTRACT: We analyze the nucleosynthesis implications of the recent discovery by M. J. Pellin and collaborators that two odd isotopes of molybdenum, 95Mo and 97Mo, are overabundant in type X SiC grains: X grains condensed within expanding supernova interiors. We find that a rapid release of neutrons (on a timescale of seconds) with fluence τ = 0.07-0.08 neutrons mbarn-1 produces the observed pattern by way of abundant production of progenitor radioactive Zr isotopes. This suggests that the condensing matter was in a supernova shell in which rapid burning was occurring at the time of ejection, probably owing to the passage of the shock wave from the core. Which shell, and the exact source of the neutrons, is still unknown, but we present a model based on the shock of an He shell.
    The Astrophysical Journal 12/2008; 540(1):L49. · 6.73 Impact Factor
  • Astrophysical Journal Letters, v.691, L20-L23 (2009). 01/2008;
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    ABSTRACT: According to standard models supernovae produce radioactive 44Ti, which should be visible in gamma-rays following decay to 44Ca for a few centuries. 44Ti production is believed to be the source of cosmic 44Ca, whose abundance is well established. Yet, gamma-ray telescopes have not seen the expected young remnants of core collapse events. The 44Ti mean life of τ ≃ 89 y and the Galactic supernova rate of ≃3/100 y imply ≃several detectable 44Ti gamma-ray sources, but only one is clearly seen, the 340-year-old Cas A SNR. Furthermore, supernovae which produce much 44Ti are expected to occur primarily in the inner part of the Galaxy, where young massive stars are most abundant. Because the Galaxy is transparent to gamma-rays, this should be the dominant location of expected gamma-ray sources. Yet the Cas A SNR as the only one source is located far from the inner Galaxy (at longitude 112°). We evaluate the surprising absence of detectable supernovae from the past three centuries. We discuss whether our understanding of SN explosions, their 44Ti yields, their spatial distributions, and statistical arguments can be stretched so that this apparent disagreement may be accommodated within reasonable expectations, or if we have to revise some or all of the above aspects to bring expectations in agreement with the observations. We conclude that either core collapse supernovae have been improbably rare in the Galaxy during the past few centuries, or 44Ti-producing supernovae are atypical supernovae. We also present a new argument based on 44Ca/40Ca ratios in mainstream SiC stardust grains that may cast doubt on massive-He-cap type I supernovae as the source of most galactic 44Ca.
    Astronomy and Astrophysics 04/2006; 450:1037-1050. · 5.08 Impact Factor
  • M. F. El Eid, L.-S. The, B. S. Meyer
    EAS Publications Series 01/2006; 19:21-30.
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    ABSTRACT: We have constructed a matrix solver for large-scale sparse matrices that arise from the treatment of nuclear burning in convective or advective environments in one dimension. We use this solver to compute nuclear abundances in a parameterized problem relevant for nucleosynthesis in supernova explosions. We discuss some details of our solutions, possible future extensions to higher dimensionality, and possible inclusion in supernova codes themselves.
    12/2005;
  • B. S. Meyer, G. C. Jordan IV
    Meteoritics and Planetary Science Supplement. 08/2004;
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    G. C. Jordan IV, B. S. Meyer
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    ABSTRACT: We demonstrate that nucleosynthesis in rapid, high-entropy expansions of proton-rich matter from high temperature and density can result in a wider variety of abundance patterns than heretofore appreciated. In particular, such expansions can produce iron-group nuclides, p-process nuclei, or even heavy, neutron-rich isotopes. Such diversity arises because the nucleosynthesis enters a little explored regime in which the free nucleons are not in equilibrium with the abundant alpha particles. This allows nuclei significantly heavier than iron to form in t he presence of abundant free nucleons early in the expansion. As the temperature drops, nucleons increasingly assemble into alpha particles and heavier nuclei. If the assembly is efficient, the resulting depletion of free neutrons allows disintegrat ion flows to drive nuclei back down to iron and nickel. If this assembly is inefficient, then the large abundance of free nucleons prevents the disintegration flows and leaves a distribution of heavy nuclei after reaction freezeout. For cases in between, an intermediate abundance distribution, enriched in p-process isotopes, is frozen out. These last expansions may contribute to the solar system's supply of the p-process nuclides if mildly proton-rich, high-entropy matter is ejected from proto-neutron stars winds or other astrophysical sites. Also sign ificant is the fact that, because the nucleosynthesis is primary, the signature of this nucleosyn thesis may be evident in metal poor stars. Comment: 11 pages, 2 tables, 1 figure. Submitted to ApJ Letters
    The Astrophysical Journal 06/2004; · 6.73 Impact Factor
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    ABSTRACT: Although the exact site for the origin of the r-process isotopes remains mysterious, most thinking has centered on matter ejected from the cores of massive stars in core-collapse supernovae [13]. In the 1970's and 1980's, however, difficulties in understanding the yields from such models led workers to consider the possibility of r-process nucleosynthesis farther out in the exploding star, in particular, in the helium burning shell [4,5]. The essential idea was that shock passage through this shell would heat and compress this material to the point that the reactions 13C(alpha; n)16O and, especially, 22Ne(alpha; n)25Mg would generate enough neutrons to capture on preexisting seed nuclei and drive an "n process" [6], which could reproduce the r-process abundances. Subsequent work showed that the required 13C and 22Ne abundances were too large compared to the amounts available in realistic models [7] and recent thinking has returned to supernova core material or matter ejected from neutron star-neutron star collisions as the more likely r-process sites.
    02/2004;
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    ABSTRACT: The alpha-rich freezeout from equilibrium occurs during the core-collapse explosion of a massive star when the supernova shock wave passes through the Si-rich shell of the star. The nuclei are heated to high temperature and broken down into nucleons and alpha particles. These subsequently reassemble as the material expands and cools, thereby producing new heavy nuclei, including a number of important supernova observables. In this paper we introduce two web-based applications. The first displays the results of a reaction-rate sensitivity study of alpha-rich freezeout yields. The second allows the interested reader to run paramaterized explosive silicon burning calculations in which the user inputs his own parameters. These tools are intended to aid in the identification of nuclear reaction rates important for experimental study. We then analyze several iron-group isotopes (59Ni, 57Co, 56Co, and 55Fe) in terms of their roles as observables and examine the reaction rates that are important in their production. Comment: 20 pages, 2 figures
    11/2002;
  • D. D. Clayton, B. S. Meyer, L. -S. The
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    ABSTRACT: We study the abundance and isotopic composition of iron in a massive-star supernova to identify those isotopic characteristics that can identify the location of the condensing matter that is contained in the presolar supernova grains from meteorites. Additional information is contained in the original extended abstract.
    05/2002;
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    ABSTRACT: r-Process yields can be extremely sensitive to expansion parameters when a persistent disequilibrium between free nucleons and alpha particles is present. This may provide a natural scenario for understanding the variation of heavy and light r-process isotopes in different r-process events. Additional information is contained in the original extended abstract.
    05/2002;
  • G. C. Jordan IV, B. S. Meyer
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    ABSTRACT: The alpha-rich freezeout from nuclear statistical equilibrium occurs during type II (core-collapse) supernovae when the shock wave passes through the Si shell of the star. The nuclei are heated to high temperature and broken down into nucleons and alpha particles. These subsequently reassemble as the material expands and cools. The alpha-rich freezeout is responsible for a number of important supernova observables. In this paper we introduce a web-based tool that displays the results of a reaction-rate sensitivity study of alpha-rich freezeout yields. This tool permits the user to identify nuclear reactions that govern the synthesis of important observables from the alpha-rich freezeout. The tool is intended to aid in the identification of nuclear reaction rates important for measurement.
    01/2002;
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    ABSTRACT: This paper evaluates the condensation of carbon solids in a gas of pure C and O atoms when these exist within the interior of an expanding young supernova. We calculate the abundances of large carbon molecules, which serve as nucleations for condensation of graphites. Additional information is contained in the original extended abstract.
    02/2001;
  • B. S. Meyer, J. E. Denny, D. D. Clayton
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    ABSTRACT: We have constructed an interactive web site that may be of interest to cosmochemists seeking to understand the evolution of isotopes in the Galaxy. The URL is http://photon.phys.clemson.edu/gce.html. Additional information is contained in the original extended abstract.
    02/2001;
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    B. S. Meyer, S. S. Gupta, L.-S. The, S. Long
    01/2001;

Publication Stats

639 Citations
79.79 Total Impact Points

Institutions

  • 2013
    • University of Chicago
      • Department of Astronomy and Astrophysics
      Chicago, Illinois, United States
  • 1993–2010
    • Clemson University
      • Department of Physics and Astronomy
      Anderson, Indiana, United States
  • 1991
    • Yeshiva University
      New York City, New York, United States