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Search for a live supernova signature of 60Fe in deep-sea sediments and a new half-life measurements of 60Fe

Wallner, A.; Feige, J.; Fifield, L. K.; Golser, R.; Kutschera, W.; Merchel, S.; Rugel, G.; Schumann, D.; Tims, S.; Winkler, S.; Sterba, J.; Bichler, M.


60Fe (2.6 My) is one of the most versatile nuclides in astrophysics. Live 60Fe was identified in the Galaxy. Its stellar production requires neutron densities available only in explosive Supernovae (SNe) or SuperAGB stars. 60Fe is also found in meteorites and indirectly via 60Ni anomalies. Fresh nucleosynthetic products may enter the Solar System (SS) trapped in cosmic dust. Hence, nearby SNe might deposit traces on Earth and since it has negligible terrestrial production, 60Fe is an ideal candidate to search for recent SNe. However, detection requires sensitivities of 60Fe/Fe~10-15 and 60Fe-AMS faces interference from stable 60Ni. So far only TU Munich, combining a MP tandem with a gas-filled magnet, measures 60Fe routinely as los as ~10-16. This group discovered live 60Fe in a deep-sea crust indicating that SNe-isotopes found their way to Earth 2-3 My ago [1]. Work is ongoing at TUM to validate this finding in other archives [2,3]. Further, Rugel et al. [4] measured a half-life substantially longer than previously recommended. We have started a similiar program at the ANU using the 14UD accelerator and a split-pole magnetic spectrograph converted into a gas-filled magnet. A substantial beamtime devoted to 60Fe has resulted in an exceptional sensitivity below 10-16. We have searched for a SN-signal in 3 deep-sea sediment cores (indian Ocean) [5]. We will present exciting new data for 60Fe with high time resolution and will relate it to potantial exposure of the SS to recent SNe. In addition, we re-measured in an independent approach the 60Fe half-life via AMS measurements of the 60 Fe/55Fe ratio.
[1] Knie et al. PRL93 (2004)
[2] Ludwig et al. this conf.
[3] Fimiani et al. LPSC 1659 (2012)
[4] Rugel et al. PRL103 (2009)
[5] Feige et al. this conf.

Keywords: accelerator mass spectrometry; supernova; radionuclide

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