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Multiple radionuclide study of a recent supernova event in deep-sea sediments with AMS
Feige, J.; Wallner, A.; Bourlès, D.; Fifield, K. L.; Korschinek, G.; Merchel, S.; Rugel, G.; Steier, P.; Tims, S.; Winkler, S. R.; Golser, R.
Long-lived radionuclides such as 26Al, 53Mn, and 60Fe are generated in massive stars and ejected into space by stellar winds and explosions. If a star ends its life in a supernova (SN) explosion close to the solar system, a fraction of these elements might be deposited in terrestrial archives. Recent analysis of a ferromanganese crust , fossilized bacteria in deep-sea sediments  and lunar samples  evidence a 60Fe concentration enhancement ~2-3 Myr ago, suggesting to originate from one or more SNe .
We expanded this work to a comprehensive and detailed study of a full set of SN-related radionuclides. Detailed depth profiles of 10Be, 26Al, 53Mn and 60Fe concentrations were measured at three different AMS laboratories for ~100 individual samples from four deep-sea sediment cores from the Indian Ocean. In contrast to our 60Fe data, which shows a clear signal without terrestrial background, a possible 26Al signal from a SN event is hidden within a non-negligible terrestrial background production. The major source of 26Al is spallogenic production by cosmic-rays in the Earth's atmosphere.
We obtained isotope ratios 26Al/27Al of ~10-14 with regularly <10% statistical uncertainty . This allowed us to generate for the first time a full history of precise 26Al data over a time period of 2 Myr for two sediment cores revealing an unexpected smooth depth dependence. We took advantage of it and applied the 26Al/27Al ratio as an independent and enhanced dating tool, comparable to 10Be/9Be but without needing stable isotope measurements. Comparative measurements of 10Be/9Be at the DREAMS and VERA facilities show a very good agreement (~5 %).
 Knie et al., Phys. Rev. Lett 93, 2004,  Ludwig et al., AMS-13,  Fimiani et al., LPSC 1659, 2012,  Feige et al., EPJWC,63 2013
Keywords: accelerator mass spectrometry; AMS; supernova; radionuclide
13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France