المؤلفون: Even, Wesley, Korobkin, Oleg, Fryer, Christopher L., Fontes, Christopher J., Wollaeger, R. T., Hungerford, Aimee, Lippuner, Jonas, Miller, Jonah, Mumpower, Matthew R., Misch, G. Wendell

المصدر: Astrophysical Journal; 8/10/2020, Vol. 899 Issue 1, p1-14, 14p

مصطلحات موضوعية: LIGHT curves, RADIOACTIVE decay, HEAVY elements, URANIUM, RARE earth metals, SCIENTISTS

مستخلص: The merger of neutron star binaries is believed to eject a wide range of heavy elements into the universe. By observing the emission from this ejecta, scientists can probe the ejecta properties (mass, velocity, and composition distributions). The emission (a.k.a. kilonova) is powered by the radioactive decay of the heavy isotopes produced in the merger and this emission is reprocessed by atomic opacities to optical and infrared wavelengths. Understanding the ejecta properties requires calculating the dependence of this emission on these opacities. The strong lines in the optical and infrared in lanthanide opacities have been shown to significantly alter the light curves and spectra in these wavelength bands, arguing that the emission in these wavelengths can probe the composition of this ejecta. Here we study variations in the kilonova emission by varying individual lanthanide (and the actinide uranium) concentrations in the ejecta. The broad forest of lanthanide lines makes it difficult to determine the exact fraction of individual lanthanides. Nd is an exception. Its opacities above 1 μm are higher than other lanthanides and observations of kilonovae can potentially probe increased abundances of Nd. Similarly, at early times when the ejecta is still hot (first day), the U opacity is strong in the 0.2–1 μm wavelength range and kilonova observations may also be able to constrain these abundances. [ABSTRACT FROM AUTHOR]

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المؤلفون: Mumpower, Matthew R.¹ mrmumpow@ncsu.edu, McLaughlin, G. C.¹ gail_mclaughlin@ncsu.edu, Surman, Rebecca² surmanr@union.edu

المصدر: Physical Review C: Nuclear Physics. Apr2012, Vol. 85 Issue 4, p1-13. 13p.

مصطلحات موضوعية: *RARE earth metals, *NUCLEOSYNTHESIS, *ENTROPY, *NEUTRONS, *RADIOACTIVE decay, *NUCLEAR physics, *NEUTRON capture

مستخلص: We study the formation and final structure of the rare-earth peak (A ∼ 160) of the r-process nucleosynthesis. Under high-entropy conditions (5 > 100kB), the rare-earth peak forms at late times in the r-process after neutron exhaustion (neutron-to-seed ratio R = 1) as matter decays back to stability. Since rare-earth peak formation does not occur during (n, γ) ⇄ (γ, n) equilibrium it is sensitive to the strong interplay between late-time thermodynamic evolution and nuclear physics input. Depending on the conditions, the peak forms either because of the pattern of the neutron capture rates or because of the pattern of the separation energies. We analyze three nuclear data sets under different thermodynamic conditions. We find that the subtleties of each nuclear data set, including separation energies and neutron capture rates, influence not only the final shape of the peak but also when it forms. We identify the range of nuclei which are influential in rare-earth peak formation. [ABSTRACT FROM AUTHOR]