THE LARGE MAGELLANIC CLOUD INTERMEDIATE-AGE GLOBULAR CLUSTER NGC 1831

NGC 1831 is one of the largest, most populous "blue globular clusters" of the LMC. A C-M diagram to V = 21.5 shows a main sequence extending up to V = 18.5 and a well-developed giant branch. Fitting to evolutionary models leads to an age estimate of 300 million years and the giants' colors suggest that [M/H] ~ — 1.0. Spectra of three cluster stars are shown. One is for one of the "anomalous giants" and it indicates that it is probably a composite image. The spectrum of the cluster shows the dominance of the hot main sequence in the integrated light.