2015ApJ...806..262L

We systematically reanalyze two previous observations of the black hole (BH) GX 339-4 in the very high and intermediate state taken with XMM-Newton and Suzaku. We utilize up-to-date data reduction procedures and implement the recently developed, self-consistent model for X-ray reflection and relativistic ray tracing, relxill. In the very high and intermediate state, the rate of accretion is high and thus the disk remains close to the innermost stable circular orbit. We require a common spin parameter and inclination when fitting the two observations since these parameters should remain constant across all states. This allows for the most accurate determination of the spin parameter of this galactic BH binary from fitting the Fe Kα emission line and provides a chance to test previous estimates. We find GX 339-4 to be consistent with a near maximally spinning BH with a spin parameter a_* > 0.97 with an inclination of 36°±4°. This spin value is consistent with previous high estimates for this object. Further, if the inner disk is aligned with the binary inclination, this modest inclination returns a high BH mass, but they need not be aligned. Additionally, we explore how the spin is correlated with the power of the jet emitted but find no correlation between the two.