  The transverse mass spectra of K0s, Lambda, Xi and Omega particles produced
in Pb-Pb collisions at 40 A GeV/c have been studied for a sample of events
corresponding to the most central 53% of the inelastic Pb-Pb cross-section. We
analyze the distributions in the framework of a parameterized model inspired by
hydrodynamics. The dependence of the freeze-out parameters on particle species
and event centrality is discussed and comparisons with results at higher energy
are shown.
