July 29, 2015 to August 6, 2015
World Forum
Europe/Amsterdam timezone

Observation of 60Fe in the Galactic Cosmic Rays

Aug 1, 2015, 2:00 PM
15m
Mississippi (World Forum)

Mississippi

World Forum

Churchillplein 10 2517 JW Den Haag The Netherlands
Oral contribution CR-EX Parallel CR10 Dir heavy

Speaker

Prof. Martin Israel (Washington University in St Louis)

Description

The Cosmic Ray Isotope Spectrometer (CRIS) on the ACE spacecraft has been measuring the isotopic composition of Galactic Cosmic Rays (GCRs) since October 1997. Using selected data from the past seventeen years, we have a set of 3.55 x 10^5 Fe nuclei in the energy interval ~240 to ~470 MeV/nucleon with excellent mass resolution characterized by sigma = 0.24 amu. In this data set we have detected fifteen well resolved iron-60 nuclei. Iron-60 is beta- unstable with a half-life 2.6 million years. The detection of these radioactive nuclei permits us to set an upper limit of a few million years on the time between nucleosynthesis of these nuclei and their acceleration to cosmic-ray energy. A lower limit of ~10^5 years was established by the CRIS observation that the electron-capture isotope nickel-59 is essentially absent in the GCRs. These two limits bracket the nucleosynthesis-to-acceleration time to a range that is consistent with the emerging evidence that the bulk of GCRs are accelerated in associations of massive stars (OB associations).
Registration number following "ICRC2015-I/" 68
Collaboration -- not specified --

Primary author

Prof. Martin Israel (Washington University in St Louis)

Co-authors

Dr Alan Cummings (California Institute of Technology) Prof. Edward Stone (California Institute of Technology) Dr Eric Christian (NASA/GSFC) Dr Georgia de Nolfo (NASA/GSFC) Dr Kelly Lave (Washington University in St. Louis) Dr Mark Wiedenbeck (Jet Propulsion Laboratory) Dr Richard Leske (California Institute of Technology) Dr Richard Mewaldt (California Institute of Technology) Dr Tycho von Rosenvinge (NASA/GSFC) Prof. Walter Binns (Washington University in St. Louis)

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