UVES and CRIRES Spectroscopy of AGB Stars: Technetium and the Third Dredge-up

Abstract

We present high-resolution UVES and CRIRES spectra of bright Oxygen-rich asymptotic giant branch (AGB) stars located in the outer galactic bulge. The UVES spectra were searched for absorption lines of the unstable element Technetium. This element is synthesised in deep layers of AGB stars, thus it is a reliable indicator of both recent s-process activity and third dredge-up. We aim to test theoretical predictions on the luminosity limit for the onset of third dredgeup. Additionally, our investigations have some implications for the age estimate of bulge AGB stars. The near-infrared spectra taken with the recently commissioned CRyogenic InfraRed Echelle Spectrograph CRIRES at ESO’s VLT aim at studying the connection between the occurrence of Tc, Carbon isotopic ratios and the luminosity of the targets.