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OB Associations, Wolf–Rayet Stars, and the Origin of Galactic Cosmic Rays

Binns, W. R. and Wiedenbeck, M. E. and Arnould, M. and Cummings, A. C. and de Nolfo, G. A. and Goriely, S. and Israel, M. H. and Leske, R. A. and Mewaldt, R. A. and Meynet, G. and Scott, L. M. and Stone, E. C. and von Rosenvinge, T. T. (2007) OB Associations, Wolf–Rayet Stars, and the Origin of Galactic Cosmic Rays. Space Science Reviews, 130 (1-4). pp. 439-449. ISSN 0038-6308. http://resolver.caltech.edu/CaltechAUTHORS:20140827-105038224

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Abstract

We have measured the isotopic abundances of neon and a number of other species in the galactic cosmic rays (GCRs) using the Cosmic Ray Isotope Spectrometer (CRIS) aboard the ACE spacecraft. Our data are compared to recent results from two-component (Wolf–Rayet material plus solar-like mixtures) Wolf–Rayet (WR) models. The three largest deviations of galactic cosmic ray isotope ratios from solar-system ratios predicted by these models, ^(12)C/^(16)O, ^(22)Ne/^(20)Ne, and ^(58)Fe/^(56)Fe, are very close to those observed. All of the isotopic ratios that we have measured are consistent with a GCR source consisting of ∼20% of WR material mixed with ∼80% material with solar-system composition. Since WR stars are evolutionary products of OB stars, and most OB stars exist in OB associations that form superbubbles, the good agreement of our data with WR models suggests that OB associations within superbubbles are the likely source of at least a substantial fraction of GCRs. In previous work it has been shown that the primary ^(59)Ni (which decays only by electron-capture) in GCRs has decayed, indicating a time interval between nucleosynthesis and acceleration of >10^5 y. It has been suggested that in the OB association environment, ejecta from supernovae might be accelerated by the high velocity WR winds on a time scale that is short compared to the half-life of ^(59)Ni. Thus the ^(59)Ni might not have time to decay and this would cast doubt upon the OB association origin of cosmic rays. In this paper we suggest a scenario that should allow much of the ^(59)Ni to decay in the OB association environment and conclude that the hypothesis of the OB association origin of cosmic rays appears to be viable.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://link.springer.com/article/10.1007/s11214-007-9195-1PublisherArticle
http://dx.doi.org/10.1007/s11214-007-9195-1DOIArticle
http://arxiv.org/abs/0707.4645arXivArticle
Additional Information:© 2007 Springer Science+Business Media B.V. Received: 5 February 2007. Accepted: 11 April 2007. Published online: 5 June 2007. The authors wish to thank J.C. Higdon and N. Prantzos for helpful discussions. This research was supported in part by the National Aeronautics and Space Administration at Caltech, Washington University, the Jet Propulsion Laboratory, and Goddard Space Flight Center (under Grants NAG5-6912 and NAG5-12929).
Group:Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NASANAG5-6912
NASANAG5-12929
Washington UniversityUNSPECIFIED
JPLUNSPECIFIED
Goddard Space Flight CenterUNSPECIFIED
Subject Keywords:ISM: cosmic rays, Stars: Wolf–Rayet
Record Number:CaltechAUTHORS:20140827-105038224
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140827-105038224
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48985
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:27 Aug 2014 18:16
Last Modified:28 Aug 2014 21:59

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