AAS 201st Meeting, January, 2003
Session 46. Planetary Systems: Observations and Models
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[46.03] The Metallicity Histograms For Stars With Planets and Other Nearby Dwarfs

B. J. Taylor, K. Croxall (BYU)

Seven years ago, Taylor (1994, PASP 106, 704) published an [Fe/H] catalog based on a statistical analysis of literature data for class IV-V FGK stars. An updated version of that catalog (Taylor, submitted for publication) has now been used to investigate the metallicities of volume-limited samples of nearby dwarfs. Following Haywood (2001, MNRAS 325, 1365), an interim allowance is made for sampling bias against metal-rich stars. In addition, the following improvements over previous analyses are made: a) data for more than 500 stars are analyzed, b) rigorous rms errors from the catalog are used, c) inferences are drawn only from formal statistical tests (and not from graphs), d) the Benjamini-Hochberg algorithm (see Miller et al. 2001, AJ 122, 3492) is used to test multiple hypotheses, and e) zero-skewness histograms are used (when required) to allow for a low-metallicity tail produced by thick-disk stars.

Favata et al. (1997, A&A 323, 809) have found an apparent difference between mean metallicities for hot and cool dwarfs. Allowance for sampling bias reduces this difference to marginal statistical significance. The local mean value of [Fe/H] is not found to differ from zero at 95% confidence, though that mean value is higher than a counterpart for a magnitude-limited sample of giants (see Taylor 1999, A&A 362, 563; Table 5). For stars known to have planets (SWPs), the mean value of [Fe/H] is found to be about 0.2 dex higher than that for other stars, as noted by previous authors. The zero-difference hypothesis is rejected with a false-alarm probability of less than 7 x 10-5. At 95% confidence, however, no difference is found between the rms widths of the histograms for SWPs and other stars. This result does not seem to have been noted previously in print.

This research has been supported by the BYU College of Physical and Mathematical Sciences.

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