R-process Pattern in the Very-metal-poor Halo Star Cs 31082-001

The very-metal-poor halo star CS 31082-001 was discovered to be very strongly r-process-enhanced during the course of a VLT+UVES high-resolution follow-up of metal-poor stars identified in the HK survey of Beers & colleagues. Both the strong n-capture element enhancement and the low carbon and nitrogen content of the star (reducing the CN molecular band contamination) led to the first U abundance measurement in a stellar spectrum (Cayrel et al. 2001), and the opportunity to use both radioactive species U and Th for dating the progenitor to this star. However, age computations all rely on the hypothesis that the r-process pattern is solar, as this was indeed observed in the other famous r-process-enhanced very metal poor stars CS 22892-052 (Sneden et al. 1996, 2000) and in HD115444 (Westin et al. 2000). Here, we investigate whether this hypothesis is verified also for CS 31082-001, using a preliminary analysis of over 20 abundances of n-capture elements in the range Z=38 to Z=92. Cayrel et al. (2001; this volume) discuss the discovery and importance of CS 31082-001, and here we report a summary of a preliminary abundance analysis for this star (Table 1). The n-capture element abundances (relative to iron, [X/Fe]) of CS 31082001 are compared in Fig. 1-a to those of CS 22892-052 and HD115444, showing that the overabundance of the Z>56 n-capture elements in CS31082-001 is almost identical to that of CS 22892-052, with a mean overabundance of [X/Fe]∼+1.7dex. These two stars are therefore the most extreme cases of ncapture element enhancement in halo stars, far more extreme than HD115444. Furthermore, the abundance pattern of the 5670 seems to be more abundant in CS31082-001 than