Published in

American Astronomical Society, Research Notes of the American Astronomical Society, 3(5), p. 47, 2021

DOI: 10.3847/2515-5172/abee77

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No Black Holes in NGC 6397

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Red circle
Preprint: archiving forbidden
Red circle
Postprint: archiving forbidden
Green circle
Published version: archiving allowed
Data provided by SHERPA/RoMEO

Abstract

Abstract Recently, Vitral & Mamon detected a central concentration of dark objects in the core-collapsed globular cluster NGC 6397, which could be interpreted as a subcluster of stellar-mass black holes. However, it is well established theoretically that any significant number of black holes in the cluster would provide strong dynamical heating and is fundamentally inconsistent with this cluster's core-collapsed profile. Claims of intermediate-mass black holes in core-collapsed clusters should similarly be treated with suspicion, for reasons that have been understood theoretically for many decades. Instead, the central dark population in NGC 6397 is exactly accounted for by a compact subsystem of white dwarfs (WDs), as we demonstrate here by inspection of a previously published model that provides a good fit to this cluster. These central WD subclusters are in fact a generic feature of core-collapsed clusters, while central black hole subclusters are present in all non-collapsed clusters.