(Proposal ID) S15A-093

(PI) Aoki, Wako

(Proposal Title)
 Subaru/HDS study of very metal-poor stars found with LAMOST

(Abstract)
We propose to obtain R~ 36,000 spectra of 100 candidate very metal-poor stars 
([Fe/H] <~-2.5) in the Milky Way halo found with LAMOST to search for stars 
that present chemical signatures of first-generation stars and to investigate 
the statistics of low-mass stars in the extremely low-metallicity range ([Fe/H]
<~-3). Recent discovery of a very metal-poor star ([Fe/H]=-2.5) having a 
peculiar abundance pattern suggests that nucleosynthesis yields of first-
generation very massive stars could have been recorded in very metal-poor 
stars, along with Ultra Metal-Poor ([Fe/H]<~-4) stars, for which only several 
examples are known to date. Statistics obtained from high-resolution spectra 
of very metal-poor stars includes the metallicity distribution function, the 
fraction of short binaries, and abundance distribution of heavy neutron-
capture elements (Sr and Ba). Following the great success of the first 
Subaru/HDS follow-up spectroscopy in S14A (two nights) for 54 stars found 
with LAMOST, we propose to extend the HDS observations to about 100 stars 
selected from the LAMOST sample that includes relatively bright candidates 
of very metal-poor stars in the Galactic halo. This is an ideal sample to 
investigate the above issues.