Classification of Gaia-ESO Survey Giraffe/HR15n stellar spectra in the gamma2 Vel cluster | Francesco Damiani

We present new spectral diagnostics available from HR15n spectra of stars in the gamma2 Vel cluster, useful for classification and determination of fundamental stellar parameters. We define several spectroscopic indices, sampling the amplitude of TiO bands, the H-alpha line core and wings, and temperature- and gravity-sensitive sets of lines, each useful as a temperature or gravity indicator over a limited range of stellar spectral types. H-alpha line indices are also useful as chromospheric activity or accretion indicators. Using these indices we find a clear difference between gravity of main-sequence field stars and pre-main-sequence cluster stars, as well as a much larger difference between these latter and giant stars. We discuss the usefulness of these results to measure ages of young clusters. We discuss the effect of classical T-Tauri star veiling on the defined indices, finding that veiling may be relevant for only few stars in the gamma2 Vel sample. We also discuss the calibration of the new temperature and gravity indices.