We present results from spectral fitting of the very high state of GX 339-4 with NuSTAR and Swift .
We use relativistic reflection modeling to measure the spin of the black hole and inclination of the inner disk , and find a spin of a = 0.95 ^ { +0.02 } _ { -0.08 } and inclination of 30 ° \pm 1 ( statistical errors ) .
These values agree well with previous results from reflection modelling .
With the exceptional sensitivity of NuSTAR at the high-energy side of the disk spectrum , we are able to constrain multiple physical parameters simultaneously using continuum fitting .
By using the constraints from reflection as input for the continuum fitting method , we invert the conventional fitting procedure to estimate the mass and distance of GX 339-4 using just the X-ray spectrum , finding a mass of 9.0 ^ { +1.6 } _ { -1.2 } M _ { \odot } and distance of 8.4 \pm 0.9 kpc ( statistical errors ) .