2003PASP..115.1367V

We present abundances of Ti, Fe, and Ni as well as 10 post-iron-peak elements in two Galactic S stars, S UMa and Stephenson 1303. Based upon the presence or absence of Tc in their spectra, S UMa is an intrinsic S star and Stephenson 1303 is an extrinsic S star. Both stars are slightly metal-poor and at high Galactic latitude; they thus make an interesting comparison as well as a further test of current models of nucleosynthesis in low-mass stars. In addition, the abundance ratio of heavy to light s-process elements, [hs/ls], correlates with the metallicities of Stephenson 1303 and S UMa as expected if the ¹³C neutron source drives the s-process.