Cosmogenic nuclides in the Košice meteorite: Experimental investigations and Monte Carlo simulations |
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Authors: | Pavel P Povinec Jozef Masarik Ivan Sýkora Andrej Ková?ik Juraj Beňo Matthias M M Meier Rainer Wieler Matthias Laubenstein Vladimir Porub?an |
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Institution: | 1. Department of Nuclear Physics and Biophysics, Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia;2. Department of Earth Sciences, ETH Zürich, Zürich, Switzerland;3. Centre de Recherches Pétrographiques et Géochimiques, CNRS Nancy, Vand?uvre les Nancy, France;4. National Laboratory of Gran Sasso, INFN, I‐67100, Assergi (AQ), Italy;5. Department of Astronomy, Physics of the Earth and Meteorology, Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia;6. Astronomical Institute, Slovak Academy of Sciences, Bratislava, Slovakia |
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Abstract: | Results of nondestructive gamma‐ray analyses of cosmogenic radionuclides (7Be, 22Na, 26Al, 46Sc, 48V, 54Mn, 56Co, 57Co, 58Co, and 60Co) in 19 fragments of the Ko?ice meteorite are presented and discussed. The activities varied mainly with position of fragments in the meteoroid body, and with fluxes of cosmic‐ray particles in the space affecting radionuclides with different half‐lives. Monte Carlo simulations of the production rates of 60Co and 26Al compared with experimental data indicate that the pre‐atmospheric radius of the meteoroid was 50 ± 5 cm. In two Ko?ice fragments, He, Ne, and Ar concentrations and isotopic compositions were also analyzed. The noble‐gas cosmic‐ray exposure age of the Ko?ice meteorite is 5–7 Myr, consistent with the conspicuous peak (or doublet peak) in the exposure age histogram of H chondrites. One sample likely contains traces of implanted solar wind Ne, suggesting that Ko?ice is a regolith breccia. The agreement between the simulated and observed 26Al activities indicate that the meteoroid was mostly irradiated by a long‐term average flux of galactic cosmic rays of 4.8 particles cm?2 s?1, whereas the short‐lived radionuclide activities are more consistent with a flux of 7.0 protons cm?2 s?1 as a result of the low solar modulation of the galactic cosmic rays during the last few years before the meteorite fall. |
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