Survey for transiting extrasolar planets in stellar systems. II. Spectrophotometry and metallicities of open clusters

We present metallicity estimates for seven open clusters based on spectrophotometric indices from moderate-resolution spectroscopy. Observations of field giants of known metallicity provide a correlation between the spectroscopic indices and the metallicity of open cluster giants. We use chi(2) analysis to fit the relation of spectrophotometric indices to metallicity in field giants. The resulting function allows an estimate of the target-cluster giants' metallicities with an error in the method of +/- 0.08 dex. We derive the following metallicities for the seven open clusters: NGC 1245, [M/H] = -0.14 +/- 0.04; NGC 2099, [M/H] = -0.05 +/- 0.05; NGC 2324, [M/H] = -0.06 +/- 0.04; NGC 2539, [M/H] = -0.04 +/- 0.03; NGC 2682 (M67), [M/H] = -0.05 +/- 0.02; NGC 6705, [M/H] = +0.14 +/- 0.08; NGC 6819, [M/H] = -0.07 +/- 0.12. These metallicity estimates will be useful in planning future extrasolar planet transit searches, since planets may form more readily in metal-rich environments.