Chandra Observation of the Globular Cluster NGC 6440 and the Nature of Cluster X-ray Luminosity Functions

David Pooley; Walter H. G. Lewin; Frank Verbunt; Lee Homer; Bruce Margon; Bryan M. Gaensler; Victoria M. Kaspi; Jon M. Miller; Derek W. Fox; Michiel van der Klis

doi:10.1086/340498

arXiv · astro-ph/0111212

Chandra Observation of the Globular Cluster NGC 6440 and the Nature of Cluster X-ray Luminosity Functions

David Pooley·Walter H. G. Lewin·Frank Verbunt·Lee Homer·Bruce Margon·Bryan M. Gaensler·Victoria M. Kaspi·Jon M. Miller·Derek W. Fox·Michiel van der Klis

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Abstract

As part of our campaign to determine the nature of the various source populations of the low-luminosity globular cluster X-ray sources, we have obtained a Chandra X-ray Observatory ACIS-S3 image of the globular cluster NGC 6440. We detect 24 sources to a limiting luminosity of ~2 times 10^31 erg/s (0.5-2.5keV) inside the cluster's half-mass radius, all of which lie within ~2 core radii of the cluster center. We also find excess emission in and around the core which could be due to unresolved point sources. Based upon X-ray luminosities and colors, we conclude that there are 4-5 likely quiescent low-mass X-ray binaries and that most of the other sources are cataclysmic variables. We compare these results to Chandra results from other globular clusters and find the X-ray luminosity functions differ among the clusters.

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David Pooley, Walter H. G. Lewin, Frank Verbunt, Lee Homer, Bruce Margon, Bryan M. Gaensler, Victoria M. Kaspi, Jon M. Miller, Derek W. Fox, Michiel van der Klis. 2002-03-28. Chandra Observation of the Globular Cluster NGC 6440 and the Nature of Cluster X-ray Luminosity Functions. https://doi.org/10.1086/340498

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