EDP Sciences
Free Access
Issue
A&A
Volume 555, July 2013
Article Number L3
Number of page(s) 6
Section Letters
DOI https://doi.org/10.1051/0004-6361/201321818
Published online 08 July 2013

Online material

Appendix A: Table A.1 and Figs. A.1−A.4

Table A.1

Sample of early massive AGBs: spectroscopic Teff and derived Li, Rb, and Zr abundancesa.

thumbnail Fig. A.1

High-resolution optical spectra (in black) and best model fits (in red) in the Li I 6708 Å region (left panel) and Rb I 7800 Å region (right panel) for the AGB stars RU Ari, R Cen, SV Cas, and RU Cyg. The derived Li and Rb abundances (in the usual scale log N(X) + 12) are indicated. Synthetic spectra obtained for Li and Rb abundances shifted +0.5 dex (in blue) and −0.5 dex (in green) (these values are ±1.0 for Li in R Cen and SV Cas) from the adopted values are also shown. We note that Li is not detected in the extreme OH/IR AGB star RU Ari, which displays a strong Rb I line that is not detected in the other stars.

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thumbnail Fig. A.2

High-resolution optical spectra (in black) and best model fits (in red) in the ZrO 6474 Å region (left panel) and the Tc I 5924 Å region (right panel) for the AGB stars RU Ari, SV Cas, and RU Cyg. The derived Zr abundances and Tc upper limits (in the usual scale log N(X) + 12) are indicated. Synthetic spectra obtained for Zr abundances shifted +0.5 dex (in blue) and −0.5 dex (in green) from the adopted values are also shown. For the less sensitive Tc I 5924 Å line, synthetic spectra obtained for Tc abundances shifted +5.0 dex (in blue) are shown. We note that none of the stars are in our sample is found to be enriched in Zr or Tc.

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thumbnail Fig. A.3

High-resolution optical spectra of the non-Tc AGB star R Cen (in black; this paper) and the Tc AGB star S Her (in red; taken from Uttenthaler et al. 2011) around the Tc I line at 4238 Å. The wavelength of the Tc line is marked with a dashed vertical line. We note that S Her displays a strong Tc I line that is completely absent in R Cen.

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thumbnail Fig. A.4

Temporal evolution of the Li, Rb, Zr, and Tc abundances as predicted by the HBB-MLT 5 M model with a 13C-rich region (the 13C pocket) and a delayed superwind (Karakas et al. 2012). We include a 13C pocket by inserting protons into the top of the He-intershell (with a mass = 1 × 10-4  M) at the deepest extent of each TDU episode. We refer to Karakas et al. (2012) and Lugaro et al. (2012) for details of this procedure. Tc (also Zr although at a slower rate) is quickly produced by the 13C neutron source; log ε(Tc) > 0 at the beginning of the super Li-rich phase (log ε(Li) ~ 4). The evolution of Rb is not greatly affected by the inclusion of the 13C pocket, but Zr is more affected, being even more abundant than Rb during the super Li-rich phase. We note that the Tc abundance is an upper limit because the trend of the half-life of 99Tc, decreasing with the temperature, is not included. However, the difference would be very small because the 99Tc half-life changes only from terrestrial 0.22 Myr to 0.11 Myr at the temperature of 100 MK typical of the 13C pocket, which means that 99Tc behaves as a stable nucleus during this neutron flux.

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© ESO, 2013

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