Although there have been recent claims that there is a large dispersion in the abundances of the heavy neutron capture elements in the old Galactic globular cluster M92, we show that the measured dispersion for the absolute abundances of four of the
rare earth elements within a sample of 12 luminous red giants in M92 (less than or equal to 0.07 dex) does not exceed the relevant sources of uncertainty. As expected from previous studies, the heavy elements show the signature of the r-process. Their abundance ratios are essentially identical to those of M30, another nearby globular cluster of similar metallicity.
NGC 2419 is a massive outer halo Galactic globular cluster whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419 with Keck/HIRES at reasonable SNR. One
of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic globular clusters, represented here by a sample of giants in the nearby globular cluster M30. Although our measurements show that NGC 2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo globular clusters.
We present a new solution for the dispersive element in astronomical spectrographs, which in many cases can provide an upgrade path to enhance the spectral resolution of existing moderate-resolution reflection-grating spectrographs. We demonstrate th
at in the case of LRIS-R at the Keck 1 Telescope a spectral resolution of 18,000 can be achieved with reasonable throughput under good seeing conditions.
We present an abundance analysis based on high dispersion and high signal-to-noise ratio Keck spectra of a very highly microlensed Galactic bulge dwarf, OGLE-2007-BLG-349S, with Teff ~ 5400 K. The amplification at the time the spectra were taken rang
ed from 350 to 450. This bulge star is highly enhanced in metallicity with [Fe/H] = +0.51 pm 0.09 dex. The abundance ratios for the 28 species of 26 elements for which features could be detected in the spectra are solar. In particular, there is no evidence for enhancement of any of the alpha-elements including O and Mg. We conclude that the high [Fe/H] seen in this star, when combined with the equally high [Fe/H] derived in previous detailed abundance analysis of two other Galactic bulge dwarfs, both also microlensed, implies that the median metallicity in the Galactic bulge is very high. We thus infer that many previous estimates of the metallicity distribution in the Galactic bulge have substantially underestimated the mean Fe-metallicity there due to sample bias, and suggest a candidate mechanism for such. If our conjecture proves valid, it may be necessary to update the calibrations for the algorithms used by many groups to interpret spectra and broad band photometry of the integrated light of very metal-rich old stellar populations, including luminous elliptical galaxies.
