The Phosphorus, Sulfur, Argon, and Calcium Isotopic Composition of the Galactic Cosmic Ray Source

Details The Phosphorus, Sulfur, Argon, and Calcium Isotopic Composition of the Galactic Cosmic Ray Source The Phosphorus, Sulfur, Argon, and Calcium Isotopic Composition of the Galactic Cosmic Ray Source

Apr 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009apj...695..666o&link_type=abstract

The Astrophysical Journal, Volume 695, Issue 1, pp. 666-678 (2009).

Astronomy and Astrophysics

Astronomy

3

Cosmic Rays, Galaxy: Abundances, Ism: Abundances, Ism: Bubbles, Supernovae: General

Scientific paper

Galactic cosmic ray (GCR) measurements of the phosphorus, sulfur, argon, and calcium isotopes made by the Cosmic Ray Isotope Spectrometer aboard the Advanced Composition Explorer are reported over the energy range from ~100 to ~400 MeV nucleon-1. The propagation of cosmic rays through the Galaxy and heliosphere is modeled with constraints imposed by measurements. Isotopic source abundance ratios 31P/32S, 34S/32S, 38Ar/36Ar, and 44Ca/40Ca are deduced. The derived 31P/32S ratio is 2.34 ± 0.34 times larger than the solar system value, lending further credence to the suggestion that refractory elements are enriched in the GCRs due to the sputtering of ions off grains in the cores of superbubbles. By determining the GCR source abundances of argon (a noble gas) and calcium (a refractory), it is determined that material in grains is accelerated to GCR energies a factor of 6.4 ± 0.3 more efficiently than gas-phase material in this charge range. With this information, the dust fraction of phosphorus and sulfur in the interstellar material that is mixed with stellar ejecta to form the GCR seed material is found to be consistent with astronomical observations.

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