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Recherche de signatures isotopiques dans les sediments marins de l'explosion d'une supernova proche du system solaire

Abstract : The recent observation of an 60Fe peak in a deep-sea ferromanganese crust has been interpreted as due to a supernova explosion relatively close to the solar system 2.8 ° 0.4 Myr ago. To confirm this interpretation with better time-resolved measurements, and the simultaneous access, on the same sample, to other isotopes and geochemical phases, marine sediments seem to be a tool of choice. The objective of this work was to search for isotopic anomalies which would be characteristic for residues of this supernova. More specifically, 129I, 60Fe, and 26Al have been investigated, being measured by Accelerator Mass Spectrometry (AMS). Quantifying these nuclides' fluxes would help constrain stellar nucleosynthesis models. These residues are isotopes initially produced during hydrostatic and/or explosive nucleosynthesis. The physical conditions during the explosion (temperature, neutron density) are such that supernovae are thought to be good candidates for the astrophysical site of the r-process.
The 129I study showed that measurement of pre-anthropogenic 129I/127I ratios need a very strict control of the various potential 129I sources, especially when working with small quantities (micrograms) of iodine. This study revealed that the expected pre-anthropogenic 129I/127I ratio for pre-nuclear samples in the marine environment shows a large discrepancy between theoretical calculations and experimental measurements. 60Fe and 26Al measurements allow us to conclude that, in the authigenic phase of the marine sediments, there is no 60Fe anomaly in the time interval defined by the signal found on the Fe-Mn crust (from 2.4 to 3.2 Myr), and no 26Al anomaly from 2.6 to 3.2 Myr.
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Caroline Fitoussi. Recherche de signatures isotopiques dans les sediments marins de l'explosion d'une supernova proche du system solaire. Astrophysique [astro-ph]. Université Paris Sud - Paris XI, 2006. Français. ⟨tel-00125431⟩

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