VLT-UVES analysis of 5 giants in 47 Tucanae

Abstract

High resolution spectra of 5 giants, including a horizontal branch star, of the metal-rich globular cluster 47 Tucanae were obtained with the UVES spectrograph at the 8m VLT UT2-Kueyen telescope. The atmospheric parameters (Teff, log g, [Fe/H], vt) were derived from VIJK photometry and spectroscopic data based on Fe I and Fe II lines. Fe I and Fe II iron abundances and respective total errors [Fe I/H] = –0.66 ± 0.12 and [Fe II/H] = –0.69 ± 0.24 are found. Abundances of α (O, Mg, Ca, Si, Ti), odd-Z (Na, Al), s- (Ba, La, Zr), and r-process (Eu) elements were determined by means of spectrum synthesis. The main results are [O/Fe] = +0.35 ± 0.11, [Mg/Fe] ≈ [Si/Fe] ≈ [Ti/Fe]=+0.23 ± 0.17, [Ca/Fe] = 0.0 ± 0.15, [Ba/Fe] = +0.31 ± 0.22 and [Eu/Fe] = +0.33 ± 0.10. Overabundances of the α-elements O, Mg, Si and Ti, and of Eu are similar to those seen in halo metal-poor stars, whereas a solar Ca-to-Fe ratio resembles the values found in bulge stars. An overall metallicity Z = 0.006 or [M/H] = –0.45 is thus obtained, as is a mean heliocentric radial velocity vhel r = −22.43 ± 1.99 km sˉ¹.