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We probe models of disc truncation in the hard spectral state of an outburstof the well-known X-ray transient GX 339--4. We test a large number ofdifferent models of disc reflection and its relativistic broadening, using twoindependent sets of codes, and apply it to a \textit{Rossi X-ray TimingExplorer} spectrum in the rising part of the hard state of the 2010/11outburst. We find our results to be significantly model-dependent. While all ofthe models tested show best-fits consistent with truncation, some models allowthe disc to extend close to the innermost stable circular orbit (ISCO) and somerequire substantial disc truncation. The different models yield a wide range inbest-fit values for the disc inclination. Our statistically best model has aphysical thermal Comptonization primary continuum, requires the disc to betruncated at a radius larger than or equal to about two ISCO radii for themaximum dimensionless spin of 0.998, and predicts a disc inclination inagreement with that of the binary. Our preferred models have moderate Feabundance, $\gtrsim$2 times solar. We have also tested the effect of increasingthe density of the reflecting medium. We find it leads to an increase in thetruncation radius, but also to an increase in the Fe abundance, opposite to aprevious finding.

Comparison of spectral models for disc truncation in the hard state of GX 339-4