Ultraviolet Observations by the IUE of 31 Clusters of the Large Magellanic Cloud

Abstract

Ultraviolet observations of 31 star clusters of the Large Magellanic Cloud obtained by the International Ultraviolet Explorer are presented. The clusters, mostly globular, span the range of ages from about 10 to the 7th to 10 to the 10th yr. The sample includes several young globular clusters, which have no counterpart in the Galaxy. The paper is devoted to the study of the basic properties of the clusters in the ultraviolet, such as the interstellar reddening, the spatial extension in the ultraviolet, and the ultraviolet color indices. These data are essential for a later study of the evolutionary stage of the clusters. One important result of this study is that a discontinuity exists in the UV two-color diagram, a fact which deserves further investigation, since it might support the suggestion made by other authors that an active star formation phase took place in the Large Magellanic Cloud starting about 100 million yr ago.