Abstract
For most elements, the isotopic ratios seen in cosmic rays (CRs) are similar to those in the solar wind. The most important exception to this is 22Ne/20Ne where the CR value is ∼ 5 times that of the solar wind. According to most recent models of nucleosynthesis, a large amount of 22Ne is generated in Wolf-Rayet (WR) stars. In the winds of carbon sequence of WR stars, i.e., WC stars, the isotopic ratio 22Ne/20Ne can be much larger than in the solar wind. Here, we consider CRs produced by 22Ne-enriched WR winds in young massive star clusters assuming the acceleration occurs from an ensemble of shock waves from the massive stars’ winds. We estimate the fraction of all Galactic CRs such sources may produce for a given set of parameters.
Highlights
The origin of Galactic cosmic rays (GCRs) is a long-standing problem of the theoretical and observational astrophysics
The chemical composition of GCRs has been investigated with several experiments (IMP7[13], ISEE-3[14], Voyager[15], ACE-CRIS[16] and others), while the solar wind composition was deeply studied by determining meteoritic CI chondrite abundance
In this work we suggest that young massive star clusters can be a significant source of GCRs and enhanced 22Ne/20Ne
Summary
The origin of Galactic cosmic rays (GCRs) is a long-standing problem of the theoretical and observational astrophysics. Other galactic sources, such as pulsars and stellar winds, are certain to contribute at some level. Strong stellar winds from massive stars are a likely source [3, 4, 5, 6, 7, 8, 9, 10]) and this acceleration will be enhanced in compact star clusters of massive stars where acceleration can take place by the ensemble of shocks from multiple winds [11, 12]. In the solar wind 22Ne/20Ne = 0.07, while in GCRs 22Ne/20Ne = 0.387 ± 0.027, which corresponds to 22Ne enhancement by a factor of 5.3 ± 0.3 [16]
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