Judith G. Cohen, Norbert Christlieb, Ian Thompson, Andrew McWilliam, Stephen Shectman
We have now completed detailed abundance analyses of more than 100 stars
selected as candidate extremely metal-poor stars with [Fe/H] < -3.0 dex. Of
these 18 are below -3.3 dex on the scale of the First Stars VLT project led by
Cayrel, and 57 are below -3.0 dex on that scale. Ignoring enhancement of carbon
which ranges up to very large values, and two C-rich stars with very high N as
well, there are 0 to 3 high or low strong outliers for each abundance ratio
tested from Mg to Ni. The outliers have been checked and they are real.
Ignoring the outliers, the dispersions are in most cases approximately
consistent with the uncertainties, except those for [Sr/Fe] and [Ba/Fe], which
are much larger. Approximately 6% of the sample are strong outliers in one or
more elements between Mg and Ni. This rises to ~15% if minor outliers for these
elements and strong outliers for Sr and Ba are included. There are 6 stars with
extremely low [Sr/Fe and [Ba/Fe], including one which has lower [Ba/H] than
Draco 119, the star found by Fulbright, Rich and Castro to have the lowest such
ratio known previously. There is one extreme r-process star.
View original:
http://arxiv.org/abs/1201.4190
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