We have obtained a high resolution ( R \sim 90 , 000 ) spectrum of the carbon- and s -process-element-rich , very metal-poor ( [ Fe/H ] = -2.7 ) subgiant LP 625-44 , as well as that of HD 140283 ( a metal-poor subgiant with normal abundance ratio ) for comparison , with the High Dispersion Spectrograph ( HDS ) for the Subaru Telescope for detailed abundance study .
The spectrum covers 3400-7800Å and enables us to study important spectral lines which had not been detected in the previous works .
We found significant overabundances in some light elements , in addition to carbon and nitrogen for which large enhancements were already known .
The oxygen abundance derived from the O I triplet around 7770Å is uncertain , but the excess of oxygen in LP 625-44 seems remarkable ( perhaps by nearly a factor 10 ) , in comparison with that of HD 140283 derived from the same lines .
The Na enhancement in LP 625-44 is by about a factor 50 , suggesting hydrogen burning in the ^ { 22 } Ne-rich layer in an asymptotic giant branch star which produces the abundance pattern of this object .
In our new spectrum of LP 625-44 , the Pb I \lambda 3683Å line has been detected , as well as the Pb I \lambda 4057Å line which has already been studied , confirming the Pb abundance ( \log \epsilon ( Pb ) \sim 1.9 ) derived by the previous work .
The abundance ratio of s -process elements at the second peak ( e.g. , La , Ce and Nd ) to that at the third peak ( Pb ) in LP 625-44 is significantly higher ( by a factor 5 ) than that in other three s -process element-rich objects recently studied by van Eck et al..
Recent theoretical works have modeled the s -process nucleosynthesis in the radiative layer of asymptotic giant branch stars in the inter-pulse phase , and the above results means that these processes produced a large scatter in the abundance ratios .
Another possiblity is that different processes ( e.g. , s -process nucleosynthesis during thermal pulses ) have contributed to heavy elements in the early Galaxy .