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Originally published in Science Express on 9 November 2006
Science 15 December 2006:
Vol. 314. no. 5806, pp. 1751 - 1754
DOI: 10.1126/science.1133706
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Reports

Rubidium-Rich Asymptotic Giant Branch Stars

D. A. García-Hernández1*{dagger}, P. García-Lario1,2, B. Plez3, F. D'Antona4, A. Manchado5 and J. M. Trigo-Rodríguez6,7

1 ISO Data Centre, European Space Astronomy Centre, Research and Scientific Support Department, European Space Agency, Villafranca del Castillo, Apdo. 50727, E-28080 Madrid, Spain.
2 Herschel Science Centre, European Space Astronomy Centre, Research and Scientific Support Department, European Space Agency, Villafranca del Castillo, Apdo. 50727, E-28080 Madrid, Spain.
3 Groupe de Recherches en Astronomie et Astrophysique du Languedoc, UMR 5024, Université de Montpellier 2, F-34095 Montpellier Cedex 5, France.
4 INAF–Osservatorio Astronomico di Roma, via Frascati 33, I-00040 MontePorzio Catone, Italy.
5 Instituto de Astrofísica de Canarias and Consejo Superior de Investigaciones Científicas, La Laguna, E-38200 Tenerife, Spain.
6 Institute of Space Sciences and Consejo Superior de Investigaciones Científicas, Campus UAB, Facultat de Ciències, Torre C-5, parells, 2a planta, 08193 Bellaterra, Barcelona, Spain.
7 Institut d'Estudis Espacials de Catalunya, Ed. Nexus, Gran Capità 2-4, 08034 Barcelona, Spain.


Figure 1 Fig. 1. Best model fit and observed spectra around the Rb I line at 7800.3 Å. Shown are observed spectra (in black) and the best model fit (in red) of four sample stars (IRAS 05098-6422, IRAS 18429-1721, IRAS 06300+6058, and IRAS 19059-2219) with an effective temperature of 3000 K but with very different Rb abundances: [Rb/Fe] = +0.1, +1.2, +1.6, and +2.3 dex, respectively. Note that the Rb I resonance line has a clear "blue-shifted" circumstellar component in the Rb-rich star IRAS 06300+6058. [View Larger Version of this Image (41K GIF file)]
 

Figure 2 Fig. 2. Observed Rb abundances (squares) versus OH expansion velocity. One upper limit to the Rb abundance is shown with a dot. The abundance estimates that correspond to the photospheric abundance needed to fit the stellar component are shown with triangles. A maximum error bar of ±0.8 dex is also shown for comparison. The star with high OH expansion velocity and no Rb, which does not follow the general behavior observed, is IRAS 19147+5004 (TZ Cyg). This star possibly is a non-AGB star, as it is not a long-period, Mira-like variable. [View Larger Version of this Image (16K GIF file)]
 

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