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A. Sozzetti, D. W. Latham, G. Torres, R. P. Stefanik (CfA), A. P. Boss (CIW), B. W. Carney (UNC), J. B. Laird (BGSU)
Among the two proposed scenarios for gas giant planet formation, core accretion can be enhanced in metal-rich stars, while disk instability is insensitive to the primordial metallicity of the protoplanetary disk. If the two competing mechanisms for gas giant planet formation produce significantly different distributions of planet masses and orbital elements, this could then be verified by looking at such properties as a function of metallicity. However, the low-metallicity stellar sample is at present too small to test but the most glaring discrepancies between such hypothetical populations. A spectroscopic survey to search for giant planets orbiting an unbiased sample of metal-poor stars is therefore an essential element for helping a) to understand whether the idea that planets form preferentially around the most metal-rich stars is correct or it should be questioned, b) to determine whether core accretion or disk instability is the dominant formation mechanism for gas giant planets, or to verify the existence of bimodal planet formation, and c) to better understand the dependence of migration processes on the metallicity of the protoplanetary disk.
We present results from our ongoing spectroscopic search for giant planets within 1 AU around a well-defined sample of metal-poor stars with HIRES on the Keck 1 telescope. We have achieved an rms radial velocity precision of ~12 m/s over a time-span of 12 months. We place preliminary upper limits on the detectable companion mass as a function of orbital period. In particular, the data collected so far build toward evidence of the absence of very short-period (a few days) giant planets, and are consistent with the existence of a Brown Dwarf desert extended to the low metallicity regime.
A. S. acknowledges support from the Smithsonian Astrophysical Observatory through the SAO Predoctoral Fellowship program.
The author(s) of this abstract have provided an email address for comments about the abstract: asozzetti@cfa.harvard.edu
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Bulletin of the American Astronomical Society, 36 #2
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