We present a broad band spectral analysis of the black hole binary GX 339-4 with NuSTAR and Swift using high density reflection model .
The observations were taken when the source was in low flux hard states ( LF ) during the outbursts in 2013 and 2015 , and in a very high flux soft state ( HF ) in 2015 .
The high density reflection model can explain its LF spectra with no requirement for an additional low temperature thermal component .
This model enables us to constrain the density in the disc surface of GX 339-4 in different flux states .
The disc density in the LF state is \log ( n _ { e } / cm ^ { -3 } ) \approx 21 , 100 times higher than the density in the HF state ( \log ( n _ { e } / cm ^ { -3 } ) = 18.93 ^ { +0.12 } _ { -0.16 } ) .
A close-to-solar iron abundance is obtained by modelling the LF and HF broad band spectra with variable density reflection model ( Z _ { Fe } = 1.50 ^ { +0.12 } _ { -0.04 } Z _ { \odot } and Z _ { Fe } = 1.05 ^ { +0.17 } _ { -0.15 } Z _ { \odot } respectively ) .