Chemical abundances in the inner 5 kpc of the Galactic disk

High-resolution, high signal-to-noise spectral data are presented for four young B-type stars lying towards the Galactic Centre. Determination of thei r atmospheric parameters from their absorption line profiles, and uvby phot ometric measurement of the continua indicate that they are massive objects lying slightly out of the plane, and were probably born in the disk between 2.5-5 kpc from the Centre. We have carried out a detailed absolute and dif ferential line-by-line abundance analyses of the four stars compared to two stars with very similar atmospheric parameters in the solar neighbourhood. The stars appear to be rich in all the well sampled chemical elements (C, N, Si, Mg, S, Al), except for oxygen. Oxygen abundances derived in the atmo spheres of these four stars are very similar to that in the solar neighbour hood. If the photospheric composition of these young stars is reflective of the gaseous ISM in the inner Galaxy, then the values derived for the enhan ced metals are in excellent agreement with the extrapolation of the Galacti c abundance gradients previously derived by Rolleston et al. (2000) and oth ers. However, the data for oxygen suggests that the inner Galaxy may not be richer than normal in this element, and the physical reasons for such a sc enario are unclear.