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Context. Extremely reddened asymptotic giant branch stars (AGB) lose mass at high rates of >10-5 M⊙ yr-1. This is the very last stage of AGB evolution, in which stars in the mass range ~2.0−4.0 M⊙ (for solar metallicity) should have been converted to C stars already. The extremely reddened AGB stars in the Galactic bulge are however predominantly O-rich, implying that they might be either low-mass stars or stars at the upper end of the AGB mass range.
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