First UVES observations of beryllium in very metal-poor stars

We report on a attempt to detect beryllium in two dwarf stars of the Galactic halo with metallicities below one thousandth solar. The data were obtained during the Commissioning of the Ultraviolet and Visible Echelle Spectrograph (UVES) mounted on the ESO VLT Kueyen telescope, and show the potential of UVES for studies in the UV-optical domain. We claim a beryllium detection in LP 815--43 ([Fe/H]~-2.95,[Be/H]=-13.09) at the 99.7% confidence level, while only an upper limit can be set for the second target CD -24 17504 ([Fe/H]~-3.30, [Be/H]~-13.39). These results suggest that the trend of beryllium with metallicity keeps decreasing as lower metallicities are probed, with no evidence for flattening. In CD -24 17504 we also analyzed the Li I line at 6708A, and derived a lithium abundance close to the Spite plateau.