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Chandra Observation of the Globular Cluster NGC 6440 and the Nature of Cluster X‐Ray Luminosity Functions

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

Pooley et al. 2002 The Astrophysical Journal 573 184.

  • Provider: AAS Journals

Caption: Fig. 2.

X‐ray color‐magnitude diagram. The X‐ray color is defined as the logarithm of the ratio of Xsoft (0.5–1.5 keV) corrected counts to Xhard (1.5–6.0 keV) corrected counts, and the magnitude is the logarithm of Xmed (0.5–4.5 keV) corrected counts. For the sake of clarity, only a few error bars are shown; they represent the 1 σ error estimates given by Gehrels (1986). Our correction for photoelectric absorption has the effect of uniformly shifting the data +0.48 units on the left axis and +0.64 units on the bottom axis. The top and right axes provide the absorbed color and magnitude scales (superscript a), i.e., the observed colors and magnitudes uncorrected for absorption. CX 22 is not shown since it has 0 counts in X﹩_{\mathrm{soft}\,}﹩.

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