Ultraviolet Imaging of the Globular Cluster 47 Tucanae

Robert W. O'Connell; Ben Dorman; Ronak Y. Shah; Robert T. Rood; Wayne B. Landsman; Ralph C. Bohlin; Susan G. Neff; Morton S. Roberts; Andrew M. Smith; Theodore P. Stecher

doi:10.1086/118619

arXiv · astro-ph/9704042

Ultraviolet Imaging of the Globular Cluster 47 Tucanae

Robert W. O'Connell·Ben Dorman·Ronak Y. Shah·Robert T. Rood·Wayne B. Landsman·Ralph C. Bohlin·Susan G. Neff·Morton S. Roberts·Andrew M. Smith·Theodore P. Stecher

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Abstract

We have used the Ultraviolet Imaging Telescope to obtain deep far-UV (1620 Angstrom), 40' diameter images of the prototypical metal-rich globular cluster 47 Tucanae. We find a population of about 20 hot (Teff > 9000 K) objects near or above the predicted UV luminosity of the hot horizontal branch (HB) and lying within two half-light radii of the cluster center. We believe these are normal hot HB or post-HB objects rather than interacting binaries or blue stragglers. IUE spectra of two are consistent with post-HB phases. These observations, and recent HST photometry of two other metal-rich clusters, demonstrate that populations with rich, cool HB's can nonetheless produce hot HB and post-HB stars. The cluster center also contains an unusual diffuse far-UV source which is more extended than its V-band light. It is possible that this is associated with an intracluster medium, for which there was earlier infrared and X-ray evidence, and is produced by C IV emission or scattered light from grains.

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Robert W. O'Connell, Ben Dorman, Ronak Y. Shah, Robert T. Rood, Wayne B. Landsman, Ralph C. Bohlin, Susan G. Neff, Morton S. Roberts, Andrew M. Smith, Theodore P. Stecher. 1997-04-03. Ultraviolet Imaging of the Globular Cluster 47 Tucanae. https://doi.org/10.1086/118619

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