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We present the optical/infra-red lightcurve (O/IR) of the black hole X-raybinary GX 339-4 collected at the SMARTS 1.3m telescope from 2002 to 2010.During this time the source has undergone numerous state transitions includinghard-to-soft state transitions when we see large changes in the near-IR fluxaccompanied by modest changes in optical flux, and three rebrightening eventsin 2003, 2005 and 2007 after GX 339-4 transitioned from the soft state to thehard. All but one outburst show similar behavior in the X-rayhardness-intensity diagram. We show that the O/IR colors follow two distincttracks that reflect either the hard or soft X-ray state of the source. Thus,either of these two X-ray states can be inferred from O/IR observations alone.From these correlations we have constructed spectral energy distributions ofthe soft and hard states. During the hard state, the near-IR data have the samespectral slope as simultaneous radio data when GX 339-4 was in a bright opticalstate, implying that the near-IR is dominated by a non-thermal source, mostlikely originating from jets. Non-thermal emission dominates the near-IR bandsduring the hard state at all but the faintest optical states, and the fractionof non-thermal emission increases with increasing optical brightness. Thespectral slope of the optical bands indicate that a heated thermal source ispresent during both the soft and hard X-ray states, even when GX 339-4 is atits faintest optical state. We have conducted a timing analysis of the lightcurve for the hard and soft states and find no evidence of a characteristictimescale within the range of 4-230 days.

Optical and Near Infrared Monitoring of the Black-Hole X-ray Binary GX 339-4 During 2002-2010