Chandra observation of the globular cluster NGC 6440 and the nature of cluster X-ray luminosity functions

David Pooley, Walter H.G. Lewin, Frank Vereunt, 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 × 10 31 ergs s-1 (0.5-2.5 keV) 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 that could be due to unresolved point sources. Based on 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.

Original languageEnglish (US)
Pages (from-to)184-196
Number of pages13
JournalAstrophysical Journal
Volume573
Issue number1 I
DOIs
StatePublished - Jul 1 2002

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Pooley, D., Lewin, W. H. G., Vereunt, F., Homer, L., Margon, B., Gaensler, B. M., Kaspi, V. M., Miller, J. M., Fox, D. W., & Van Der Klis, M. (2002). Chandra observation of the globular cluster NGC 6440 and the nature of cluster X-ray luminosity functions. Astrophysical Journal, 573(1 I), 184-196. https://doi.org/10.1086/340498