Red Giants with Extreme Mental Deficiencies.

Abstract

The three field stars, HD 122563, HD 165195, and HD 221170, similar to giants in metal-poor globular clusters, show decreases in the average metal/ hydrogen ratios by factors of 800, 500, and 500, respectively, compared with the sun. The abundance ratios of other elements to iron resemble those in the sun, with important exceptions. Manganese and vanadium are deficient with respect to iron, by a factor of 3. In HD 122563 all elements heavier than zinc are deficient compared with iron by a factor of 50, yielding a total deficiency of about 50000 for the heavy elements. These observations are interpreted by assuming that the elements were synthesized from hydrogen early in the history of our Galaxy. These stars were formed when the interstellar medium was almost entirely hydrogen, between 10/sup 7/ and 10/sup 9/ years after star formation began. Their metallic constituents were formed and ejected from massive, rapidly evolving stars of extremely low metal content. Processing at high temperatures synthesized the elements from sodium through nickel which are now present in all three stars. The material that went into HD 122563 is drastically deficient in all elements produced by the addition of neutrons to the iron peak, whereasmore » light elements produced by neutron addition---aluminum and scandium--exist in normal amounts or are only slightly deficient. We interpret this to mean that when a flux of free neutrons became available, the progenitors of the light s-process elements were present, but the iron peak elements were rare or absent. The europium in HD 122563 may have been produced by the s-process, a very unexpected result. The presence of europium in HD 165195, in at least the normal ratio to the other elements, raises difficulties concerning r-process nucleosynthesis, since type I supernovae of small mass may not have begun to appear at the early epoch when the star was formed. 37 references. (auth)« less