Abundances of disk and bulge giants from high-resolution optical spectra. V. Molybdenum: The p-process element

Abstract

Aims: In this work, we aim to make a differential comparison of the neutron-capture and p-process element molybdenum (Mo) in the stellar populations in the local disk(s) and the bulge, focusing on minimising possible systematic effects in the analysis.
Methods: The stellar sample consists of 45 bulge and 291 local disk K-giants observed with high-resolution optical spectra. The abundances are determined by fitting synthetic spectra using the Spectroscopy Made Easy (SME) code. The disk sample is separated into thin and thick disk components using a combination of abundances and kinematics. The cosmic origin of Mo is investigated and discussed by comparing with published abundances of Mo and the neutron-capture elements cerium (Ce) and europium (Eu).
Results: We determine reliable Mo abundances for 35 bulge and 282 disk giants with a typical uncertainty of [Mo/Fe] ~ 0.2 and ~0.1 dex for the bulge and disk, respectively.
Conclusions: We find that the bulge is possibly enhanced in [Mo/Fe] compared to the thick disk, which we do not observe in either [Ce/Fe] or [Eu/Fe]. This might suggest a higher past star-formation rate in the bulge; however, as we do not observe the bulge to be enhanced in [Eu/Fe], the origin of the molybdenum enhancement is yet to be constrained. Although the scatter is large, we may be observing evidence of the p-process contributing to the heavy element production in the chemical evolution of the bulge.

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