Astron. Astrophys. 336, L61-L64 (1998)

Letter to the Editor

Evidence from Voyager and ISEE-3 spacecraft

Data for the decay of secondary K-electron capture isotopes during the propagation of cosmic rays in the Galaxy

A. Soutoul ¹, R. Legrain ¹, A. Lukasiak ², F.B. McDonald ² and W.R. Webber <sup>3

1</sup> DAPNIA/SAp,SPhN CEA/SACLAY, F-91191 Gif-sur-Yvette CEDEX, France
² Institute for Physical Sciences and Technology, University of Maryland
³ Astronomy Department New Mexico State University, Las Cruces, NM

Received 31 July 1997 / Accepted 12 May 1998

Abstract

New data from the cosmic ray experiment on the Voyager spacecraft confirms and extends earlier data from a similar experiment on the ISEE-3 spacecraft which indicates the possibility of the decay of certain K-capture isotopes during the interstellar propagation of galactic cosmic rays. These cosmic ray measurements, along with the cross section measurements, indicate that 25% of the K-capture isotopes ⁵¹Cr and ⁴⁹V produced as secondaries have decayed at interstellar energy of 400 MeV/nuc. This suggests a possible interstellar energy gain 100 MeV/nuc out of the current interstellar energy 500 MeV/nuc. This measurement suggests that the study of the K-capture isotopes may now have reached a level that will soon provide definitive information on the amount of re-acceleration that may occur during cosmic-ray propagation after an initial acceleration in the cosmic ray sources.

Key words: ISM: cosmic rays

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. Calculation of the characteristic decay times of K-capture isotopes
• 3. The data and its interpretation
• 4. Other K-capture isotopes
• 5. Summary and conclusions
• References

© European Southern Observatory (ESO) 1998

Online publication: July 27, 1998
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