Analysis of the Hot Stellar Population of the Globular Cluster ω Centauri

Abstract

We analyze the far-UV and Stro mgren u photometric data of the globular cluster u Cen presented in an earlier paper. The color-magnitude diagram of the cluster from these two bands shows that u Cens horizontal-branch (HB) consists of a group of cooler intermediate blue HB (IBHB) and a group of extreme HB (EHB) stars, together with a large population of post-HB stars. Unexpected features in the diagram are a discontinuity between the EHB and IBHB objects lying at an (FUV [ 3500) 0 D [1.5, unusually large population of stars below the EHB, and a number of sources bluer than an innite temperature blackbody.