出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：Recent large surveys of metal-poor stars in the Galaxy have revealed that a surprising fraction are
enhanced in their carbon-to-iron ratios by factors of 10-10,000 relative to the solar ratio. Although
the carbon overabundances in most of the stars in the metallicity interval −2.7≤ [Fe/H]≤−2.0
are likely to have arisen from Asymptotic Giant Branch processing (and subsequent dumping via
mass transfer to a surviving companion), there exist many stars with [Fe/H] < −3.0 (including
the two lowest [Fe/H] stars known, with [Fe/H] < −5.0) that may not be accounted for by this
process. Rather, primordial (or nearly primordial) progenitors are implicated.
We report on the existing information from present surveys, including cool giants from the recently
completed HERES (Hamburg/ESO R-process Enhanced Star) survey, and from warm
main-sequence turnoff stars selected from SDSS-I. We also describe the results that will come
from the recently-funded extension of the SDSS, which includes the program SEGUE: Sloan Extension
for Galactic Understanding and Exploration. SEGUE will identify some 20,000 stars with
[Fe/H] < −2.0, several thousand of which are expected to be carbon enhanced.
