Francesca Primas

Lead abundance in the uranium star CS 31082-001

In a previous paper we were able to measure the abundance of uranium and thorium in the very-metal poor halo giant BPS CS 31082-001, but only obtained an upper limit for the abundance of lead (Pb). We have got from ESO 17 h of additional exposure on this star in order to secure a detection of the minimum amount of lead expected to be present in CS 31082-001, the amount arising from the decay of the original content of Th and U in the star. We report here this successful detection. We find an LTE abundance log (Pb/H) + 12 = −0.55 ± 0.15 dex, one dex below the upper limits given by other authors for the similar stars CS 22892-052 and BD +17 ◦ 3248, also enhanced in r-process elements. From the observed present abundances of Th and U in the star, the expected amount of Pb produced by the decay of 232 Th, and 238 U alone, over 12-15 Gyr is −0.73±0.17 dex. The decay of 235 Ui s more difficult to estimate, but is probably slightly below the contribution of 238 U, making the contribution of the 3 actinides only slightly below, or even equal to, the measured abundance. The contribution from the decay of 234 Uh as was not included, for lack of published data. In this sense our determination is a lower limit to the contribution of actinides to lead production. We comment this result, and we note that if a NLTE analysis, not yet possible, doubles our observed abundance, the decay of the 3 actinides will still represent 50 per cent of the total lead, a proportion higher than the values considered so far in the literature.

Beryllium Abundances in a New Set of Halo Stars

We present observations of the Be II 3130 A resonance doublet in 15 halo stars with metallicities ranging from [Fe/H]=−0.4 to −3.2 obtained with the CASPEC spectrograph with a FWHM≈0.09 A resolution at the ESO 3.6m telescope. Abundances are derived by means of the synthetic spectra technique employing Kurucz (1993) atmospheric models, with enhanced α-elements and no overshooting. The derived abundances show that Be correlates linearly with iron, giving strength to previous results. Three stars are found to be Be deficient. It is also shown that Be observations are useful to discriminate strongly Li-depleted stars and to follow the lithium galactic evolution.

HST-STIS abundances in the uranium-rich very metal-poor star CS 31082-001

The abundance derivation of heavy r-elements may provide a better understanding of the r-process, and the determination of several reference r-elements should allow a better determination of the star’s age. The spatial ultraviolet (UV) region presents a large number of lines of heavy elements, and in some cases such as Bi, Pt, Au, detectable lines are only available in the UV. The extreme “r-process star” CS 31082-001 ([Fe/H] =−2.9) was observed in the spatial UV in order to determine abundances of the heavy elements, using STIS on board HST.

EXECUTIVE COMMITTEE WORKING GROUP: WOMEN IN ASTRONOMY

The gender† dimension of science and technology has become one of the most important and debated issues worldwide, impacting society at every level. A variety of international initiatives on the subject have been undertaken, including the continued monitoring of the status of women in science by Unesco Institute for Statistics (UIS) or the annual reports “Education at a Glance” by the Organization for Economic Co-operation and Development (OECD) as well as field-related working groups and networking in order to collect data in a consistent manner. The majority of the international organizations have made clear statements about their discrimination policies (independently of their main field(s) of action), including the International Council for Science whose regulations are followed by the IAU. Gender equality at large is one of the eight United Nations Millennium Development Goals, which clearly calls for action related to science, technology and gender.