2003/12/27 by Andrew McWilliam, R. Michael Rich, McWilliam, Andrew +1
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #History and Developments in Astronomy #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0312628
contributed paper to Carnegie Observatories Astrophysics Series, Volume 4: Origin and Evolution of the Elements, A.McWilliam and M. Rauch (eds.) http://www.ociw.edu/symposia/symposium4/proceedings.html
arxiv created 2003/12/27 · openalex publication_date 2003/12/27 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present detailed abundance results for 9 Galactic bulge stars in Baade's Window, based on HIRES (R=45,000--60,000) spectra taken with the Keck I telescope. The alpha elements show non-uniform enhancements relative to the Solar neighborhood trends: Mg and Si are enhanced in all our bulge stars by ∼0.5--0.3 dex, showing a slight decrease with increasing [Fe/H]. Oxygen is enhanced in most bulge stars, similar to the Galactic halo, but the [O/Fe] ratios suddenly decline beginning at [Fe/H]=-0.5 dex, with a slope consistent with no oxygen production in the bulge for [Fe/H]≥-0.5 dex. The observed production of magnesium in the absence of oxygen synthesis appears to be inconsistent with current predictions for supernova nucleosynthesis yields; we suggest that this may be connected to the Wolf-Rayet phenomenon, which occurs in the pertinent metallicity range. The trend of [Ti/Fe] shows an enhancement relative to the solar neighborhood of ∼0.3 dex, but declines somewhat by solar metallicity; thus, the Ti trend is less extreme than found by McWilliam amp; Rich (1994, MR94). For metal-poor bulge stars calcium is enhanced by ∼0.3 dex, similar to the Galactic halo, but in our bulge stars with [Fe/H]≥-0.5, Ca show a slight deficiency relative to the solar neighborhood value, consistent with the findings of MR94; this may indicate a slightly top-heavy IMF as suggested by MR94 and McWilliam (1997). Aluminum is enhanced in all our Galactic bulge giant stars by ∼0.25 dex; we argue that this is consistent with nucleosynthesis dominated by type II supernova events (SNII), implied by the Mg and Si enhancements. (Abridged)