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The Ages of Galactic Bulge Stars with Realistic Uncertainties
Meridith Joyce, Christian I. Johnson, Tommaso Marchetti +3
Using modern isochrones with customized physics and carefully considered statistical techniques, we recompute the age distribution for a sample of 91 micro-lensed dwarfs in the Gal…
HST observations of the globular cluster NGC 6402 (M14) and its peculiar multiple populations
Francesca D'Antona, Antonino P. Milone, Christian I. Johnson +6
We present Hubble Space Telescope (HST) photometric results for NGC 6402, a highly reddened very luminous Galactic globular cluster (GC). Recent spectroscopic observations of its r…
The Most Metal-poor Stars in Omega Centauri (NGC 5139)
Christian I. Johnson, Andrea K. Dupree, Mario Mateo +3
The most massive and complex globular clusters in the Galaxy are thought to have originated as the nuclear cores of now tidally disrupted dwarf galaxies, but the connection between…
Light Element Discontinuities Suggest an Early Termination of Star Formation in the Globular Cluster NGC 6402 (M14)
Christian I. Johnson, Nelson Caldwell, R. Michael Rich +2
NGC 6402 is among the most massive globular clusters in the Galaxy, but little is known about its detailed chemical composition. Therefore, we obtained radial velocities and/or che…
Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569
Christian I. Johnson, R. Michael Rich, Nelson Caldwell +4
Photometric and spectroscopic analyses have shown that the Galactic bulge cluster Terzan 5 hosts several populations with different metallicities and ages that manifest as a double…
Light and Heavy Element Abundance Variations in the Outer Halo Globular Cluster NGC 6229
Christian I. Johnson, Nelson Caldwell, R. Michael Rich +1
NGC 6229 is a relatively massive outer halo globular cluster that is primarily known for exhibiting a peculiar bimodal horizontal branch morphology. Given the paucity of spectrosco…