Fine analysis of the A0 Ia-O supergiant HD 7583 in the Small Magellanic Cloud.

Summary. A model atmosphere analysis of HD 7583, an extreme A 0 Ia-O Supergiant in the "wing" of the Small Magellanic Cloud has been done by evaluating 7 high dispersion spectra in the range 3500< <6600 A (12.3 and 31.3 A/mm) taken at ESO, La Silla. The observations are best fitted by a model atmosphere (radiative equilibrium, LTE, no line blanketing) with the parameters Te =89600 and logg =0.87 and a depth dependent micro turbulence. The resulting metal abundance distribution is the same as for galactic A- super- giants and HD 33579 in the LMC within the accuracy of the analysis. A tentative chromospheric model was worked out for the interpretation of the He-absorption lines and the strong and red shifted variable . The bolometric correction is B.C. =0.19. The luminosity is L/L0 500000, the radius is R/R0 295, and the mass is /A0 24. HD 7583 is in the He-burning evolution stage with an evolution time tE 5.4. 106 (years) and fits in an independent age determination of the wing of the SMC. The results of the abundance determination are discussed in connection with the theoretical framework of the chemical evolution of the galaxies and the general validity of cepheids as distance indicators. Key words: fine analysis - abundance determination - supergiant - stellar chromosphere - Small Magellanic Cloud