2006/07/17 by Katia Cunha, Kátia Cunha, Verne V. Smith
Physics and Astronomy · #Astro and Planetary Science #Gamma-ray bursts and supernovae #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/507673
published as Astrophys.J.651:491-501,2006 · ApJ in press
arxiv created 2006/07/17 · openalex publication_date 2006/10/27 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
We present chemical abundances in K and M red giant members of the Galactic bulge derived from high-resolution infrared spectra obtained with the Phoenix spectrograph on Gemini-South. The elements studied are carbon, nitrogen, oxygen, sodium, titanium, and iron. The evolution of C and N abundances in the studied red giants shows that their oxygen abundances represent the original values with which the stars were born. Oxygen is a superior element for probing the timescale of bulge chemical enrichment via [O/Fe] versus [Fe/H]. The [O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with [O/Fe] values falling above those of the disk. Titanium also behaves similarly to oxygen with respect to iron. Based on these elevated values of [O/Fe] and [Ti/Fe] extending to large Fe abundances, it is suggested that the bulge underwent a more rapid chemical enrichment than the halo. In addition, there are declines in both [O/Fe] and [Ti/Fe] in those bulge targets with the largest Fe abundances, signifying another source affecting chemical evolution: perhaps supernovae of Type Ia. Sodium abundances increase dramatically in the bulge with increasing metallicity, possibly reflecting the metallicity-dependent yields from supernovae of Type II, although Na contamination from H-burning in intermediate-mass stars cannot be ruled out.