A grid of synthetic spectra and indices Fe5270, Fe5335, Mgb and Mg$_\mathsf{2}$ as a function of stellar parameters and [ $\mathsf{\alpha}$/Fe]

We have computed a grid of synthetic spectra in the wavelength range 4600-5600 A using revised model atmo- spheres, for a range of atmospheric parameters and values of (-elements/Fe)= 0: 0a nd+0.4. The Lick indices Fe5270, Fe5335, Mgb and Mg2 are measured on the grid spectra for FWHM= 2t o 8:3 A. Relations between the indices Fe5270, Fe5335 and Mg2 and the stellar parameters eective temperature Te; log g ,( Fe/H) and (/Fe), valid in the range 4000 Te 7000 K, are presented. These fitting functions are given for FWHM= 3:5 and 8.3 A. The indices were also measured for a list of 97 ref- erence stars with well-known stellar parameters observed at ESO and OHP, and these are compared to the computed indices. Finally, a comparison of the indices measured on the observed spectra and those derived from the fitting functions based on synthetic spectra is presented.

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