A grid of synthetic spectra and indices Fe5270, Fe5335, Mgb and Mg2 as a function of stellar parameters and [alpha/Fe]

We have computed a grid of synthetic spectra in the wavelength range lambda lambda 4600-5600 Å using revised model atmospheres, for a range of atmospheric parameters and values of [alpha -elements/Fe] = 0.0 and +0.4. The Lick indices Fe5270, Fe5335, Mgb and Mg₂ are measured on the grid spectra for FWHM = 2 to 8.3 Å. Relations between the indices Fe5270, Fe5335 and Mg₂ and the stellar parameters effective temperature T_eff, log ; g, [Fe/H] and [alpha /Fe], valid in the range 4000 <= T_eff <= 7000 K, are presented. These fitting functions are given for FWHM = 3.5 and 8.3 Å. The indices were also measured for a list of 97 reference 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.

Observations collected at the European Southern Observatory (ESO), La Silla, Chile and at the Observatoire de Haute Provence (OHP), St-Michel, France.

All Tables of Appendices A and B are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?/A+A/404/661