Tübingen 2003 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 7: Kern- und Teilchen-Astrophysik I
HK 7.1: Group Report
Monday, March 17, 2003, 15:45–16:15, F
Actinides and the source of cosmic rays — •B. Pfeiffer1, K.-L. Kratz1, R.E. Lingenfelter2, and J.C. Higdon3 — 1Inst. f. Kernchemie, Univ. Mainz — 2CASS, Univ. of California San Diego, La Jolla, USA — 3W.M. Keck Science Center, Claremont, USA
Supernova shocks provide the energy for the acceleration of Galactic cosmic rays, but the source material is an open question. The similarity between ultra-heavy cosmic rays (UHCR) and the interstellar medium (ISM) suggested that they may be accelerated out of the well-mixed ISM. But, since most of the heavy elements are ejected into the ISM by supernovae (SN) (which are clustered in space and time), the relative abundance ratios will not differ between these ejecta and the well-mixed ISM. However, the UHCR abundances of the actinide elements, Th, U, Pu and Cm, can provide critical constraints on the major sites of their acceleration and metallicity, as well as on the time scales involved [1].
The expected range of actinide abundances in the cosmic rays is derived from the r-process yields in core-collapse SN calculated within the “waiting-point approximation” [2]. From these yields the mean actinide abundances over time following the SN are predicted.
Future measurements of the abundance ratios will help to solve these questions. First results of experiments performed on the MIR space station (ECCO [3]) and with balloon flights (TIGER [4]) are promising.
[1] R.E. Lingenfelter et al., submitted to Ap. J.
[2] B. Pfeiffer et al., Z. Phys. A357 (1997) 235
[3] A.J. Westphal et al., Adv. Space Res. 27 (2001) 797
[4] J.T. Link et al., 27th ICRC, Hamburg, 2001