The metallicity of circumnuclear star forming regions
  We present a spectrophotometric study of circumnuclear star forming regions (CNSFR) in the early type spiral galaxies: NGC 2903, NGC 3351 and NGC 3504, all of them of over solar metallicity according to standard empirical calibrations. A detailed determination of their abundances is made after careful subtraction of the very prominent underlying stellar absorption. It is found that most regions show the highest abundances in HII region-like objects. The relative N/O and S/O abundances are discussed. In is also shown that CNSFR, as a class, segregate from the disk HII region family, clustering around smaller ``softness parameter" -- \eta' -- values, and therefore higher ionizing temperatures. 
A. I. Diaz (1), E. Terlevich (2), M. Castellanos (1 and 3) and G.F.   Hagele (1) ((1)Universidad Autonoma de Madrid, Spain (...