Publications of the Astronomical Society of Australia

Research Front: Astronomy with Radioactivities

New Attempts to Understand Nanodiamond Stardust

U. Otta1a2 c1, A. Besmehna1 p1, K. Farouqia1, O. Hallmanna1, P. Hoppea1, K.-L. Kratza1, K. Melbera3 and A. Wallnera3a4

a1 Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, D-55128 Mainz, Germany

a2 University of Western Hungary, Savaria Campus, Károlyi Gáspár tér 4, H-9700 Szombathely, Hungary

a3 University of Vienna, Faculty of Physics, VERA Laboratory, Währinger Strasse 17, A-1090 Vienna, Austria

a4 Department of Nuclear Physics, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200, Australia

Abstract

We report on a concerted effort aimed at understanding the origin and history of the pre-solar nanodiamonds in meteorites including the astrophysical sources of the observed isotopic abundance signatures. This includes measurement of light elements by secondary ion mass spectrometry (SIMS), analysis of additional heavy trace elements by accelerator mass spectrometry (AMS) and dynamic calculations of r-process nucleosynthesis with updated nuclear properties. Results obtained indicate that: (i) there is no evidence for the former presence of now-extinct 26Al and 44Ti in our diamond samples other than what can be attributed to silicon carbide and other ‘impurities’, and this does not offer support for a supernova (SN) origin but neither does it negate it; (ii) analysis by AMS of platinum in ‘bulk diamond’ yields an overabundance of r-only 198Pt that at face value seems more consistent with the neutron burst than with the separation model for the origin of heavy trace elements in the diamonds, although this conclusion is not firm given analytical uncertainties; (iii) if the Xe–H pattern was established by an unadulterated r-process, it must have been a strong variant of the main r-process, which possibly could also account for the new observations in platinum.

(Received October 25 2011)

(Accepted December 12 2011)

Keywords

  • stardust;
  • circumstellar matter;
  • isotopic ratios;
  • stars: supernovae type II;
  • ISM: kinematic and dynamics;
  • nanodiamonds

Correspondence:

c1 Corresponding author. Email: uli.ott@mpic.de

p1 Present address: Forschungszentrum Jülich GmbH, Central Division of Analytical Chemistry, D-52425 Jülich, Germany

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