Context. Extremely metal-poor (EMP) stars in the halo of the Galaxy are sensitive probes of the production of the first heavy elements and the efficiency of mixing in the early interstellar medium. The heaviest measurable elements in such stars are our main guides to understanding the nature and astrophysical site(s) of early neutron-capture nucleosynthesis. Aims. Our aim is to measure accurate, homogeneous neutron-capture element abundances for the sample of 32 EMP giant stars studied earlier in this series, including 22 stars with [Fe/H] < −3.0. Methods. Based on high-resolution, high S/N spectra from the ESO VLT/UVES, 1D, LTE model atmospheres, and synthetic spectrum fits, we determine abundances or upper limits for the 16 elements Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Yb in all stars. Conclusions. These results demonstrate that a second ("weak" or LEPP) r-process dominates the production of the lighter neutroncapture elements for [Ba/H] < −2.5. The combination of very consistent [α/Fe] and erratic [n-capture/Fe] ratios indicates that inhomogeneous models for the early evolution of the halo are needed. Our accurate data provide strong constraints on future models of the production and mixing of the heavy elements in the early Galaxy.

We present the LTE abundance analysis of high resolution spectra for red giant stars in the peculiar bulge globular cluster NGC 6388. Spectra of seven members were taken using the UVES spectrograph at the ESO VLT2 and the multiobject FLAMES facility. We exclude any intrinsic metallicity spread in this cluster: on average, [Fe/H] = −0.44 ± 0.01 ± 0.03 dex on the scale of the present series of papers, where the first error bar refers to individual star-to-star errors and the second is systematic, relative to the cluster. Elements involved in H-burning at high temperatures show large spreads, exceeding the estimated errors in the analysis. In particular, the pairs Na and O, Al and Mg are anticorrelated and Na and Al are correlated among the giants in NGC 6388, the typical pattern observed in all galactic globular clusters studied so far. Stars in NGC 6388 shows an excess of α−process elements, similar to the one found in the twin bulge cluster NGC 6441. Mn is found underabundant in NGC 6388, in agreement with the average abundance ratio shown by clusters of any metallicity. Abundances of neutron-capture elements are homogeneously distributed within NGC 6388; the [Eu/Fe] ratio stands above the value found in field stars of similar metallicity.

Aims. The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with the purpose of providing the community with a function to be used to correct the observed spectra, with an accuracy of 0.01 mag airmass −1 . Additionally, this work was meant to analyze the variability of the various components, to derive the main atmospheric parameters, and to set a term of reference for future studies, especially in view of the construction of the Extremely Large Telescope on the nearby Cerro Armazones. Methods. The extinction curve of Paranal was obtained through low-resolution spectroscopy of 8 spectrophotometric standard stars observed with FORS1 mounted at the 8.2 m Very Large Telescope, covering a spectral range 3300-8000 Å. A total of 600 spectra were collected on more than 40 nights distributed over six months, from October 2008 to March 2009. The average extinction curve was derived using a global fit algorithm, which allowed us to simultaneously combine all the available data. The main atmospheric parameters were retrieved using the LBLRTM radiative transfer code, which was also utilised to study the impact of variability of the main molecular bands of O 2 , O 3 , and H 2 O, and to estimate their column densities. Results. In general, the extinction curve of Paranal appears to conform to those derived for other astronomical sites in the Atacama desert, like La Silla and Cerro Tololo. However, a systematic deficit with respect to the extinction curve derived for Cerro Tololo before the El Chichón eruption is detected below 4000 Å. We attribute this downturn to a non standard aerosol composition, probably revealing the presence of volcanic pollutants above the Atacama desert. An analysis of all spectroscopic extinction curves obtained since 1974 shows that the aerosol composition has been evolving during the last 35 years. The persistence of traces of non meteorologic haze suggests the effect of volcanic eruptions, like those of El Chichón and Pinatubo, lasts several decades. The usage of the standard CTIO and La Silla extinction curves implemented in IRAF and MIDAS produce systematic over/under-estimates of the absolute flux.