TY - JOUR

T1 - A new abundance scale for the globular cluster 47 Tuc

AU - Koch, Andreas

AU - McWilliam, Andrew

PY - 2008/3/12

Y1 - 2008/3/12

N2 - We present chemical abundances for O, Na, Mg, Al, Si, Ca, Ti, and Fe in eight red giants and one turnoff star in the metal-rich globular cluster 47 Tuc, based on spectroscopy with the Magellan Inamori Kyocera Echelle high-resolution spectrograph on the Magellan 6.5 m Clay telescope. A robust line by a line differential abundance analysis technique, relative to the K-giant Arcturus, was used to reduce systematic errors from atmospheric and atomic parameters. Our derived mean LTE [Fe/H] of –0.76 ± 0.01 ± 0.04 dex (random and systematic error, respectively) is more metal poor by about 0.1 dex than recent literature results. The chemical element ratios in this nearby globular cluster most closely resemble those of the Galactic bulge, although there is a non-negligible overlap with the composition of thick-disk stars. We find that the [Al/Fe] and [Na/Fe] ratios coincide with the upper boundary of the trends seen in the bulge and thick disk. There is only a small intrinsic scatter in the majority of the abundance ratios, indicating that 47 Tuc is mostly a rather chemically homogeneous system.

AB - We present chemical abundances for O, Na, Mg, Al, Si, Ca, Ti, and Fe in eight red giants and one turnoff star in the metal-rich globular cluster 47 Tuc, based on spectroscopy with the Magellan Inamori Kyocera Echelle high-resolution spectrograph on the Magellan 6.5 m Clay telescope. A robust line by a line differential abundance analysis technique, relative to the K-giant Arcturus, was used to reduce systematic errors from atmospheric and atomic parameters. Our derived mean LTE [Fe/H] of –0.76 ± 0.01 ± 0.04 dex (random and systematic error, respectively) is more metal poor by about 0.1 dex than recent literature results. The chemical element ratios in this nearby globular cluster most closely resemble those of the Galactic bulge, although there is a non-negligible overlap with the composition of thick-disk stars. We find that the [Al/Fe] and [Na/Fe] ratios coincide with the upper boundary of the trends seen in the bulge and thick disk. There is only a small intrinsic scatter in the majority of the abundance ratios, indicating that 47 Tuc is mostly a rather chemically homogeneous system.

U2 - 10.1088/0004-6256/135/4/1551

DO - 10.1088/0004-6256/135/4/1551

M3 - Journal article

VL - 135

SP - 1551

EP - 1566

JO - The Astronomical Journal

JF - The Astronomical Journal

SN - 0004-6256

IS - 4

ER -