β_OX against X-ray derived hydrogen column density. In red is shown the sample presented in Fynbo et al. (2009) where the lines indicate the kernel density estimate of the distribution. For the kernel density estimate, the limits have been replaced with values. We note that contrary to what is presented in Fynbo et al. (2009), we exclude all bursts for which we do not have a redshift. Darker colours represent a higher density of points. In blue are the points for the bursts presented here along with the marginal histograms. Limits on β_OX are shown by downwards facing arrows. The corresponding marginal distributions are shown along the edges of the plot. A Kendall’s τ test, indicates a statistically significant, low degree of negative correlation (Γ = −0.21 at a p-value = 0.01).