The Interstellar Rubidium Isotope Ratio toward Rho Ophiuchi A

Abstract

The isotope ratio, 85Rb/87Rb, places constraints on models of the nucleosynthesis of heavy elements, but there is no precise determination of the ratio for material beyond the Solar System. We report the first measurement of the interstellar Rb isotope ratio. Our measurement of the Rb I line at 7800 A for the diffuse gas toward rho Oph A yields a value of 1.21 +/- 0.30 (1-sigma) that differs significantly from the meteoritic value of 2.59. The Rb/K elemental abundance ratio for the cloud also is lower than that seen in meteorites. Comparison of the 85Rb/K and 87Rb/K ratios with meteoritic values indicates that the interstellar 85Rb abundance in this direction is lower than the Solar System abundance. We attribute the lower abundance to a reduced contribution from the r-process. Interstellar abundances for Kr, Cd, and Sn are consistent with much less r-process synthesis for the solar neighborhood compared to the amount inferred for the Solar System.

12 pages with 2 figures and 1 table; will appear in ApJ Letters

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Cited by in corpus (8)

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• The Impact of Recent Advances in Laboratory Astrophysics on our Understanding of the Cosmos
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• The Interstellar N/O Abundance Ratio: Evidence for Local Infall?
• Abundances and Depletions of Neutron-Capture Elements in the Interstellar Medium
• Extragalactic 85Rb/87Rb and 6Li/7Li ratios in the Small Magellanic Cloud
• Rubidium in the Interstellar Medium