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Today's colloquium: Black Holes in Globular Clusters

Submitter: Craig Heinke (University of Alberta)
Description: I will review the searches for black holes (BHs, both stellar and intermediate-mass) in globular clusters. Searches for intermediate-mass BHs in globular clusters have not provided convincing evidence, despite heroic efforts. Bright LMXBs in extragalactic globular clusters do provide evidence for the existence of BHs in globular clusters. Recently, new discoveries of radio-bright X-ray sources in Galactic globular clusters are providing evidence for a population of low-accretion-rate black holes with surprising properties.

The globular cluster 47 Tucanae, which we now believe to possess an accreting black hole, is shown in X-rays in the above image. (Observation from the Chandra X-ray Observatory: lower-energy X-rays are red, medium-energy X-rays are green, highest-energy X-rays are blue.)
Copyright: NASA/CXC/Michigan State/A.Steiner et al
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