Speaker
Prof.
Anton Wallner
(The Australian National University)
Description
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{\small \it Nuclear Physics in Astrophysics 8, NPA8: 18-23 June 2017, Catania, Italy}
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\TITLE{$^{60}$Fe and $^{244}$Pu in deep-sea archives - a link to nearby supernova activity and r--process sites }\\[3mm]
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\AUTHORS{A. Wallner$^{1}$, N. Kinoshita$^{2}$, J. Feige$^{3}$, M. Froehlich$^{1}$, M. Hotchkis$^{4}$, L.K. Fifield$^{1}$, R. Golser$^{5}$, M. Honda$^{6}$, U. Linnemann$^{7}$, H. Matsuzaki$^{8}$, S. Merchel$^{9}$, M. Paul$^{10}$, G. Rugel$^{9}$, D. Schumann$^{10}$, S.G. Tims$^{1}$, P. Steier$^{5}$, T. Yamagata$^{12}$, S.R. Winkler$^{5}$}.
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{\small \it
\AFFILIATION{1}{Department of Nuclear Physics, The Australian National University, ACT 2601, Australia}
\AFFILIATION{2}{Institute of Technology, Shimizu Corporation, Tokyo 135-8530, Japan}
\AFFILIATION{3}{Department of Astronomy and Astrophysics, Berlin Institute of Technology, Berlin, Germany}
\AFFILIATION{4}{Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, Australia}
\AFFILIATION{5}{University of Vienna, Faculty of Physics, Isotope Research, VERA Laboratory, Austria}
\AFFILIATION{6}{Graduate School of Pure and Applied Sciences, University of Tsukuba, Japan}
\AFFILIATION{7}{Senckenberg Collections of Natural History Dresden, GeoPlasmaLab, Dresden, Germany}
\AFFILIATION{8}{MALT, The University of Tokyo, Tokyo, Japan}
\AFFILIATION{9}{Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany}
\AFFILIATION{10}{Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel}
\AFFILIATION{11}{Biology and Chemistry, Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland}
\AFFILIATION{11}{Graduate School of Integrated Basic Sciences, Nihon University, Tokyo, Japan}
}
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\centerline{Contact email: {\it anton.wallner@anu.edu.au}}
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The Interstellar Medium (ISM) is continuously fed with new nucleosynthetic products. The solar system moves through the ISM and collects dust particles. Therefore, direct detection of freshly produced radionuclides on Earth, i.e. before decaying, provide insight into recent and nearby nucleosynthetic activities [1,2]. Indeed, a pioneering work at TU Munich [3,4], which applied the ultra-sensitive single atom counting technique of accelerator mass spectrometry (AMS) to an ocean crust-sample, showed an enhanced $^{60}$Fe signal possibly of extraterrestrial origin.
Within an international collaboration [5-7] we have continued to search for ISM radionuclides incorporated in terrestrial archives. We have analyzed several deep-sea sediments, crusts and nodules for extraterrestrial $^{60}$Fe (t$_{1/2}$=2.6 Myr), $^{26}$Al (t$_{1/2}$=0.7 Myr) and $^{244}$Pu (t$_{1/2}$=81 Myr) [5-8] which are complemented by independent work at TU Munich [9-11]. All the data demonstrate a clear global $^{60}$Fe influx that is interpreted as exposure of Earth to recent ($\le${10} Myr) supernova explosions. Furthermore, the low concentrations measured for $^{244}$Pu suggest an unexpectedly low abundance of interstellar $^{244}$Pu [5]. This finding signals a rarity of actinide r--process nucleosynthesis which is incompatible with the rate and expected yield of standard core collapse supernovae as the predominant actinide-producing sites.
In this talk I will also present additional new results for $^{60}$Fe and $^{244}$Pu measured with unprecedented sensitivity. These data provide new insights into their concomitant influx and their ISM concentrations over a time period of the last 11 million years.
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{\small
[1] J. Ellis et al.,\emph{ ApJ.} \textbf{470}, 1227 (1996).
[2] G. Korschinek et al.,\emph{ Radiocarbon} \textbf{38}, 68 (1996); abstract.
[3] K. Knie et al.,\emph{ Phys. Rev. Lett.} \textbf{83}, 18 (1999).
[4] K. Knie et al.,\emph{ Phys. Rev. Lett.} \textbf{93}, 171103 (2004).
[5] A. Wallner et al.,\emph{ Nature Comm.} \textbf{6}, 5956 (2015).
[6] J. Feige et al., \emph{EPJ Web of Conf.} \textbf{63}, 3003 (2013).
[7] A. Wallner et al.,\emph{ Nature} \textbf{532}, 69 (2016).
[8] M. Paul M. et al. \emph{Astrophys. J. Lett.} \textbf{558}, L133âL135 (2001).
[9] C. Wallner et al. \emph{New Astron. Rev.} \textbf{48}, 145â150 (2004).
[10] L. Fimiani et al.,\emph{ Phys. Rev. Lett.} \textbf{116}, 151104 (2016).
[11] P. Ludwig et al.,\emph{ PNAS} \textbf{113}, 9232 (2016).}
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Primary author
Prof.
Anton Wallner
(The Australian National University)
