[3] Thomas Henry Markert et al. discovered GX 339-4 in 1973, in data obtained by the MIT Cosmic Ray Experiment on OSO-7.

In the rising phase the QPO frequency monotonically increase as the CENBOL propagates closer to the black hole and in the declining phase the QPO frequency monotonically decreases since the CENBOL recedes away from the black hole after viscosity is decreased.

The frequency variation is thus well modeled by the propagating and oscillating shock in the sub-Keplerian flow.

The entire spectrum also fits very well using two component advective flow solution.

A strong, variable relativistic jet, emitting from radio to infrared wavelengths was observed by several studies.