Title: Abundances in the globular cluster NGC 6558

Abstract: NGC 6558 is a bulge globular cluster with a blue horizontal branch (BHB), combined with 
a metallicity of [Fe/H]~-1.0. It is similar to HP 1 and NGC 6522, which could be among the oldest 
objects in the Galaxy. We analysed high-resolution spectra of four members stars observed with 
FLAMES-UVES@VLT.  We find low abundances of the odd-Z elements Na and Al, and of the 
explosive nucleosynthesis alpha-elements Si, Ca, and Ti. The hydrostatic burning alpha-elements O 
and Mg are normally enhanced as expected in old stars enriched with yields from core-collapse 
supernovae, and the iron-peak elements Mn, Cu, Zn show low abundances, which is expected for 
Mn and Cu, but not for Zn. Finally, the cluster trio NGC 6558, NGC 6522, and HP~1 show similar 
abundance patterns. 

Authors: L. Muniz, B. Barbuy, H. Ernandes, S. Ortolani, B. Dias, I. Saviane, L. Kerber, E. Bica, A. 
Perez-Villegas, L. Rossi, E.V. Held