The Time Delay before Cosmic-Ray Acceleration by Supernova Shocks
Abstract
The abundances of cosmic-ray isotopes that are produced in supernova explosions and that can decay only by electron capture are potentially useful as indicators of the time that elapses between nucleosynthesis and cosmic-ray acceleration, since after acceleration to high energy the nuclei are fully stripped of their electrons and decays are suppressed. Using data from the Cosmic Ray Isotope Spectrometer on ACE we have measured the abundances of parent and daughter nuclides in two such decays: ^59Ni → ^59Co (7.6×10^4 yr halflife) and ^57Co → ^57Fe (0.74 yr). We previously showed (ApJL 523, L61 [1999]) that if primary cosmic rays are all accelerated after a common time delay, this delay must be longer than ~10^5 yr. We now consider possible distributions of delay times and present limits on the fractions of cosmic-ray source material which could have been accelerated promptly compared to the halflives of the ^59Ni and ^57Co clocks. Implications for the origin of cosmic rays will be discussed.
- Publication:
-
APS April Meeting Abstracts
- Pub Date:
- April 2000
- Bibcode:
- 2000APS..APRW16010W