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Paper: A Large Sample Sodium and Magnesium Abundance Study in the Globular Cluster M3 (NGC 5272)
Volume: 336, COSMIC ABUNDANCES as Records of Stellar Evolution and Nucleosynthesis in honor of David L. Lambert
Page: 331
Authors: Johnson, C.I.; Sneden, C.; Pilachowski, C.A.; Guntel, B.; Kraft, R.P.; Ivans, I.I.
Abstract: We have derived sodium and magnesium abundances for more than 100 red giant branch (RGB) stars in the Galactic globular cluster M3 (NGC 5272), using moderate resolving power (R~20,000) spectra obtained with the WIYN telescope and Hydra multi-fiber spectrograph. Temperatures for the M3 sample are based on calibrations of photometric indices, in particular V − K. Gravities, microturbulent velocities, and the overall M3 metallicity ([Fe/H] ~ −1.5) are based on earlier high-resolution spectroscopic analyses. Na and Mg abundances have been determined from observed/synthetic spectrum matches of the 5682, 5688 Å Na I lines and the 5711 Å Mg I line. The resulting M3 abundances are compared with the more detailed analyses of a smaller sample of M3 RGB stars observed at very high spectral resolution with the Keck I HIRES instrument, and with a similarly large-sample data set previously obtained for M13. We conclude that the star-to-star variation in sodium is greater than that of magnesium in both clusters and also that M13 contains a higher population of low sodium, high magnesium stars than does M3.
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