Sulphur abundance in Galactic stars

¹ Liceo L. e S.P.P. S. Pietro al Natisone, annesso al Convitto Nazionale “Paolo Diacono”, Piazzale Chiarottini 8, Cividale del Friuli (Udine), Italy e-mail: elcaffau@yahoo.it
² Istituto Nazionale di Astrofisica – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy e-mail: bonifaci@ts.astro.it
³ Dipartimento di Astronomia, Università degli Studi di Trieste Trieste, via Tiepolo 11, 34131 Trieste, Italy e-mail: faraggiana@ts.astro.it
⁴ Observatoire de Paris, 64 Avenue de l'Observatoire, 75014 Paris, France
⁵ Istituto Nazionale di Astrofisica – Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy

Received: 18 February 2005
Accepted: 20 May 2005

Abstract

We investigate sulphur abundance in 74 Galactic stars by using high resolution spectra obtained at ESO VLT and NTT telescopes. For the first time the abundances are derived, where possible, from three optical multiplets: Mult. 1, 6, and 8. By combining our own measurements with data in the literature we assemble a sample of 253 stars in the metallicity range . Two important features, which could hardly be detected in smaller samples, are obvious from this large sample: 1) a sizeable scatter in [S/Fe] ratios around [Fe/H]) at low metallicities we observe stars with [S/Fe], as well as stars with higher [S/Fe] ratios. The latter do not seem to be kinematically different from the former ones. Whether the latter finding stems from a distinct population of metal-poor stars or simply from an increased scatter in sulphur abundances remains an open question.