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We analyse all available observations of GX 339--4 by XMM-Newton in the hardspectral state. We jointly fit the spectral data by Comptonization and thecurrently best reflection code, relxill. We consider in detail a contributionfrom a standard blackbody accretion disc, testing whether its inner radius canbe set equal to that of the reflector. However, this leads to an unphysicalbehaviour of the disc truncation radius, implying the soft X-ray component isnot a standard blackbody disc. This appears to be due to irradiation by thehard X-rays, which strongly dominate the total emission. We consider a largearray of models, testing, e.g., the effects of the chosen energy range, ofadding unblurred reflection, and assuming a lamppost geometry. We find theeffects of relativistic broadening to be relatively weak in all cases. In thecoronal models, we find the inner radius to be large. In the lamppost model,the inner radius is unconstrained, but when fixed to the innermost stableorbit, the height of the source is large, which also implies a weakrelativistic broadening. In the former models, the inner radius correlates withthe X-ray hardness ratio, which is consistent with the presence of a truncateddisc turning into a complete disc in the soft state. We also find the degree ofthe disc ionization to anti-correlate with the hardness, leading to strongspectral broadening due to scattering of reflected photons in the reflector inthe softest studied states.

Spectral analysis of the XMM-Newton data of GX 339-4 in the low/hard state: disc truncation and reflection