B. S. Meyer

Clemson University, CEU, South Carolina, United States

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Publications (84)110.87 Total impact

  • B. S. Meyer · M. J. Bojazi
    77th Annual Meeting of the Meteoritical-Society; 09/2014
  • T. Yu · B. S. Meyer · A. V. Fedkin · L. Grossman
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    ABSTRACT: When dense, neutron-rich layers of Type Ia supernovae mix with unburned oxygen, they can condense perovskite, a possible carrier of 48Ca and 50Ti.
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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.
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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). DOI:10.1088/0004-637X/771/1/55 · 6.28 Impact Factor
  • T. Yu · B. S. Meyer
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    ABSTRACT: Our calculation of simple models of dense thermonuclear supernovae shows that in such low entropy condition there could be a lot of n-rich isotopes produced.
  • 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.
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    T. Yu · B. S. Meyer
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    ABSTRACT: We estimate that condensates in the ejecta from dense thermonuclear supernovae will be grains of roughly 10,000 atoms. Such very small grains could be the carriers of at least some of the neutron-rich iron-group isotopes such as calcium-48.
  • B. S. Meyer · T. Yu
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    ABSTRACT: Calcium-48 has substantial production in expansions of low-entropy matter, which probably occurs in dense thermonuclear supernovae. We explore the weak statistical equilibrium in such environments to constrain their neutron richness.
  • T. Yu · B. S. Meyer
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    ABSTRACT: We presented a simple thermonuclear (Type Ia) supernovae model that shows for high initial density (low entropy) most of the yield would be neutron-rich iron-group isotopes. This may help to explain the excesses and deficits correlation in FUN CAIs.
    11/2011;
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    T. Yu · B. S. Meyer
  • 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.
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    A.V. Fedkin · B.S. Meyer · L. Grossman
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    ABSTRACT: Low-density graphite spherules from the Murchison carbonaceous chondrite contain TiC grains and possess excess 28Si and 44Ca (from decay of short-lived 44Ti). These and other isotopic anomalies indicate that such grains formed by condensation from mixtures of ejecta from the interior of a core-collapse supernova with those from the exterior. Using homogenized chemical and isotopic model compositions of the eight main burning zones as end-members, Travaglio et al. (1999) attempted to find mixtures whose isotopic compositions match those observed in the graphite spherules, subject to the condition that the atomic C/O ratio = 1. They were partially successful, but this chemical condition does not guarantee condensation of TiC at a higher temperature than graphite, which is indicated by the spherule textures. In the present work, model compositions of relatively thin layers of ejecta within the main burning zones computed by Rauscher et al. (2002) for Type II supernovae of 15, 21 and 25 Mʘ are used to construct mixtures whose chemical compositions cause equilibrium condensation of TiC at a higher temperature than graphite in an attempt to match the textures and isotopic compositions of the spherules simultaneously. The variation of pressure with temperature and the change in elemental abundances with time due to radioactive decay were taken into account in the condensation calculations. Layers were found within the main Ni, O/Ne, He/C and He/N zones that, when mixed together, simultaneously match the carbon, nitrogen and oxygen isotopic compositions, 44Ti/48Ti ratios and inferred initial 26Al/27Al ratios of the low-density graphite spherules, even at subsolar 12C/13C ratios. Due to the relatively large proportion of material from the Ni zone and the relative amounts of the two layers of the Ni zone required to meet these conditions, predicted 28Si excesses are larger than observed in the low-density graphite spherules, and large negative δ46Ti/48Ti, δ47Ti/48Ti, δ49Ti/48Ti and δ50Ti/48Ti are produced, in contrast to the observed normal δ46Ti/48Ti and δ47Ti/48Ti, large positive δ49Ti/48Ti and smaller positive δ50Ti/48Ti. Although better matches to the observed δ46Ti/48Ti, δ47Ti/48Ti and 28Si excesses can be found using much smaller amounts of Ni zone material and some Si/S zone material, it is very difficult to match simultaneously the Ti and Si isotopic compositions in any mixtures of material from these deep layers with He/C and He/N zone material, regardless of the condensation sequence. The occurrence of Fe-rich, Si-poor metal grains inside the graphite spherules does not have a satisfactory explanation.
    Geochimica et Cosmochimica Acta 06/2010; DOI:10.1016/j.gca.2010.03.021 · 4.25 Impact Factor
  • A. V. Fedkin · B. S. Meyer · L. Grossman · S. J. Desch
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    ABSTRACT: ^44Ti-rich TiC condenses before graphite in SN ejecta only if thin sub-layers of the main burning zones mix together; such mixing is also needed to form Fe-olivine. High-T phases change from carbides to oxides along composition gradients within the He/N zone.
  • B. S. Meyer · D. D. Clayton · and L.-S. The
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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. DOI:10.1086/312865 · 6.28 Impact Factor
  • P. Hoppe · J. Leitner · B. S. Meyer · L. -S. The · M. Lugaro · S. Amari
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    H. Ning · Y. -Z. Qian · B. S. Meyer
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    ABSTRACT: We demonstrate that rapid expansion of the shocked surface layers of an O-Ne-Mg core following its collapse can result in r-process nucleosynthesis. As the supernova shock accelerates through these layers, it makes them expand so rapidly that free nucleons remain in disequilibrium with alpha-particles throughout most of the expansion. This allows heavy r-process isotopes including the actinides to form in spite of the very low initial neutron excess of the matter. We estimate that yields of heavy r-process nuclei from this site may be sufficient to explain the Galactic inventory of these isotopes. Comment: 11 pages, 1 figure, to appear in the Astrophysical Journal Letters
    The Astrophysical Journal 08/2007; 667(2). DOI:10.1086/522372 · 6.28 Impact Factor
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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. DOI:10.1051/0004-6361:20054626 · 4.48 Impact Factor
  • M. F. El Eid · L.-S. The · B. S. Meyer
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    ABSTRACT: We describe in a brief form present results we have obtained from a careful and up to date study of the evolution of massive stars including their advanced evolutionary phases beyond the oxygen burning phase. We describe the effects of mass loss, treatment of convection in inhomogeneous stellar layers and the rate of the C-12(alpha, gamma)O-16 reaction on the properties of stellar models in the interesting case of a 25 M-circle dot star of solar-like initial metallicity.
    EAS Publications Series 01/2006; 19:21-30. DOI:10.1051/eas:2006023
  • G. C. Jordan IV · B. S. Meyer · E. D'Azevedo
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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.
  • B. S. Meyer · G. C. Jordan IV

Publication Stats

1k Citations
110.87 Total Impact Points

Institutions

  • 1993–2013
    • Clemson University
      • Department of Physics and Astronomy
      CEU, South Carolina, United States
  • 2006
    • American University of Beirut
      • Department of Physics
      Beyrouth, Beyrouth, Lebanon
  • 1991
    • Yeshiva University
      New York City, New York, United States
  • 1990
    • Lawrence Livermore National Laboratory
      • Physics Division
      Livermore, California, United States
    • University of California, San Diego
      • Department of Physics
      San Diego, California, United States