AAS 199th meeting, Washington, DC, January 2002
Session 91. Stellar Populations and Galactic Structure
Display, Wednesday, January 9, 2002, 9:20am-6:30pm, Exhibit Hall

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[91.02] First Results on Photometric and Spectroscopic Followup of Space Interferometry Mission Grid Giant Star Candidates

J. Arenas (CTIO), D. Geisler, W. Gieren (Universidad de Concepcion), V. Smith (UTEP), S. Majewski (University of Virginia), N. Suntzeff (CTIO)

We have been awarded a NASA grant1 to obtain followup photometry and spectroscopy of the Grid Giant Star Survey (GGSS) candidates being establishing for the Space Interferometry Mission (SIM). The GGSS will yield ~ 4000 metal-poor G-K giants as SIM Astrometric Grid candidates, based on single-epoch photometry and low resolution spectroscopy. Multi-epoch photometric and spectroscopic Followup observations of these candidates are essential for verifying their astrometric stability and thus guaranteeing their utility as SIM Grid stars. These data are not only critical for the SIM project but will also allow us to improve our very limited knowledge of binary and planetary frequency in metal-poor giants. Because the kinematic properties of these stars will eventually be determined to unprecedented accuracy, a detailed understanding of their characteristics will not only be important for the SIM project, but also crucial for future studies of the GGSS database. As a scientific byproduct, the survey has already turned up hundreds of halo giants which appear very metal-poor, as well as a number of objects with very anomalous spectral characteristics. Our Folloup observations of both classes of these fascinating objects will yield their detailed abundances and astrophysical properties. This will allow us to explore chemical evolution in the Galactic halo during its earliest epoch of formation, and to determine the properties of very unusual stars. In this Meeting, we show both preliminary photometric and spectroscopic results on GGSS candidates.

1We acknowledge funding of this research from NASA/JPL through grant number NRA-99-04-OSS-058.

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