Extinct Technetium in Silicon Carbide Stardust Grains: Implications for Stellar Nucleosynthesis
Michael R. Savina,1*
Andrew M. Davis,2,3
C. Emil Tripa,1,2
Michael J. Pellin,1
Roberto Gallino,4
Roy S. Lewis,2
Sachiko Amari5
The isotopic composition of ruthenium (Ru) in individual presolar
silicon carbide (SiC) stardust grains bears the signature of
s-process nucleosynthesis in asymptotic giant branch stars,
plus an anomaly in
99Ru that is explained by the in situ decay
of technetium isotope
99Tc in the grains. This finding, coupled
with the observation of Tc spectral lines in certain stars,
shows that the majority of presolar SiC grains come from low-mass
asymptotic giant branch stars, and that the amount of
99Tc produced
in such stars is insufficient to have left a detectable
99Ru
anomaly in early solar system materials.
2 Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA.
3 Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637, USA.
4 Dipartimento di Fisica Generale, Università di Torino and Sezione INFN di Torino, I-10125 Torino, Italy.
5 Laboratory for Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130, USA.
* To whom correspondence should be addressed. E-mail: msavina{at}anl.gov
