Neutron Capture Process for a Diverse Sample of Stars

To understand the cosmic origin of heavy elements, constraints on the neutron capture (n-capture) process are imposed using stellar abundance measurements for nuclei heavier then iron (Z≥26). Examples of the n-capture process are; aging stars nearing the end of their lives (slow n-capture) and supernovae or neutron star mergers (rapid n-capture). Sites and mechanics of neutron capture production are still lacking substantial abundance observations to constrain proposed models. We are extending abundance analysis of n-capture elements in a selection of stars with diverse stellar parameters by analyzing dozens of atomic transitions in the wavelength range 3100Å-4300Å. Our sample includes spectra from 40 stars covering an overall chemical enrichment of 1/1000 solar and slightly above solar. We are analyzing: four first peak slow n-capture elements strontium (Z=38), yttrium (Z=39), zirconium (Z=40), and niobium (Z=41); and four rapid n-capture elements europium (Z=63), terbium (Z=65), thulium (Z=69), and iridium (Z=77). Three slow/rapid n-capture elements (slow n-capture process contribution ~50%) palladium (Z=46), silver (Z=47), and hafnium (Z=72) will also be measured. Our abundance measurements along with literature n-capture abundances will be compared to current stellar yields.