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OSU College of Arts and Sciences Department of Astronomy

NOTE **NEW** SPECIAL TIME/DAY!

Wednesday, February 17, 10:00 a.m.
4054 McPherson Laboratory

The Very Metal Poor Stars of the RAVE Survey

Jon Fulbright
Johns Hopkins University

The study of very metal-poor stars ("VMP stars"; defined as having [Fe/H] < -2) helps advance our understanding of the early formation of the galaxy, early supernovae, the r- and s-process, Li/Be/B and Big Bang nucleosynthesis, and the nature of the first stars. These stars are special because it is believed that they formed out of the gas enriched by only one (or a very few) of the first supernovae.

However, these stars are relatively rare and follow-up observations are best done on bright stars. The RAdial Velocity Experiment sample of nearly 300,000 spectra of I < 12 mag stars has proved an excellent source of VMP stars. We have analyzed the RAVE spectra of 543 candidate VMP stars, the large majority of which have not been identified as such to date. Of these candidates, we have found 447 stars with [Fe/H] < -2, 16 stars with [Fe/H] < -3, and 1 star with [Fe/H] < -4.

In addition, we have obtained 108 high-resolution, high-S/N spectra of these stars and have analyzed them for their detailed elemental abundances, including n-capture species. We have found new C-rich stars, s-process enhanced stars, r-process enhanced stars, etc.

An exciting result has been the discovery of 9 new Li-rich VMP giants. These bright giants (L/Lsun ~ 1000) have Li abundances up to 100 times the primordial value, and over 1000 times the Li observed in other giants of similar luminousity. Solar-metallicity Li-rich giants have been well-studied, and are known as as a phase of intermediate mass stellar evolution. Our work shows, for the first time, that these low-mass VMP giants go through a similar phase where the primary source of luminousity is the burning of Li. This result has implications on the internal mixing processes in stars, and, more importantly, whether there is an additional source of Li production (besides Big Bang nucleosynthesis) in the early universe.