How did the metals in a giant star originate?

摘要

The chemical composition of stars with extremely low metal contents (taking 'metals' to mean all elements other than hydrogen and helium) provides us with information on the masses of the stars that produced the first metals. Such a direct connection is not possible, however, if the surface of the star has been polluted by enriched material, either dredged from the star's interior or transferred from a companion star. Here we argue that, in the case of HE0107-5240 (ref. 1), the most iron-poor star known, the oxygen abundance could be a discriminant: a ratio of [O/Fe] exceeding + 3.5 would favour a pristine origin of metals, whereas an [O/Fe] ratio of less than + 3 would favour the pollution hypothesis. Using this criterion, we suggest how the required information on oxygen abundance might be obtained.