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Context: The stellar production of the light element lithium is still a matter of debate. Aims: We report the detection of low-mass, Li-rich Asymptotic Giant Branch (AGB) stars located in the Galactic bulge. Methods: A homogeneous and well-selected sample of low mass, oxygen-rich AGB stars in the Galactic bulge has been searched for the absorption lines of Li. Using spectral synthesis techniques, we determine from high resolution UVES/VLT spectra the Li abundance in four out of 27 sample stars, and an upper limit for the remaining stars. Results: Two stars in our sample have a solar Li abundance or above; these stars seem to be a novelty, since they do not show any s-element enhancement. Two more stars have a Li abundance slightly below solar; these stars do show s-element enhancement in their spectra. Different scenarios which lead to an increased Li surface abundance in AGB stars are discussed. Conclusions: Of the different enrichment scenarios presented, Cool Bottom Processing (CBP) is the most likely one for the Li-rich objects identified here. Self-enrichment by Hot Bottom Burning (HBB) seems very unlikely as all Li-rich stars are below the HBB mass limit. Also, the ingestion of a low mass companion into the stars envelope is unlikely because the associated additional effects are lacking. Mass transfer from a former massive binary companion is a possible scenario, if the companion produced little s-process elements. A simple theoretical estimation for the Li abundance due to CBP is presented and compared to the observed values.
We previously explored the circumstellar effects on the Rb and Zr abundances in massive Galactic O-rich AGB stars. Here we are interested in the role of the extended atmosphere in the case of Li and Ca. Li is an important indicator of HBB while the t
Context. Extremely reddened AGB stars lose mass at high rates of >10^-5 Msun/yr. This is the very last stage of AGB evolution, in which stars in the mass range 2.0--4.0 Msun (for solar metallicity) should have been converted to C stars already. The e
To study the nature of Bulge AGB stars and in particular their circumstellar dust, we have analysed mid-infrared spectra obtained with the ISOCAM CVF spectrometer in three Bulge fields. The ISOCAM 5-16.5 micron CVF spectra were obtained as part of th
We obtained high-resolution near-IR spectra of 45 AGB stars located in the Galactic bulge. The aim of the project is to determine key elemental abundances in these stars to help constrain the formation history of the bulge. A further aim is to link t
It is well known that thermally pulsing Asymptotic Giant Branch stars with low mass play a relevant role in the chemical evolution. They have synthesized about 30% of the galactic carbon and provide an important contribution to the nucleosynthesis of