We have observed the black hole candidate X-ray binary GX 339-4 at radio wavelengths before, during and after the 1998 high/soft X-ray state transition.We find that the radio emission from the system is strongly correlated with the hard X-ray emission and is reduced by a factor ≥ 25 during the high/soft state compared to the more usual low/hard state. At the points of state transition we note brief periods of unusually optically-thin radio emission which may correspond to discrete ejection events. We propose that in the low/hard state black hole X-ray binaries produce a quasi-continuous outflow, in the high/soft state this outflow is suppressed, and that state transitions often result in one or more discrete ejection events. Future models for low/hard states, such as ADAF/ADIOS solutions, need to take into account strong outflow of relativistic electrons from the system. We propose that the inferred Comptonising corona and the base of the jet-like outflow are the same thing, based upon the strong correlation between radio and hard X-ray emission in GX 339-4 and other X-ray binaries, and the similarity in inferred location and composition of these two components.

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We present the results of a detailed study of the high‐mass X‐ray binary 2S 0114+650 made with the pointed instruments onboard the Rossi X‐ray Timing Explorer. The spectral and temporal behaviour of this source was examined over the pulse, orbital and superorbital time‐scales, covering ∼2 cycles of the 30.7 d superorbital modulation. Marginal evidence for variability of the power‐law photon index over the pulse period was identified, similar to that observed from other X‐ray pulsars. If this variability is real it can be attributed to a varying viewing geometry of the accretion region with the spin of the neutron star. Variability of the neutral hydrogen column density over the orbital period was observed, which we attribute to the line‐of‐sight motion of the neutron star through the dense circumstellar environment. A reduction in the power‐law photon index was observed during the orbital maximum, which we speculate is due to the absorption effects as the neutron star passes behind a heavily absorbing region near the base of the supergiant companion's wind. No significant variability of the column density was observed over the superorbital period, indicating that variable obscuration by a precessing warp in an accretion disc is not the mechanism behind the superorbital modulation. In contrast, a significant increase in the power‐law photon index was observed during the superorbital minimum. We conclude that the observed superorbital modulation is tied to variability in the mass accretion rate due to some as yet unidentified mechanism.

We report radio (NRAO VLA and Australia Telescope Compact Array), soft X-ray (Rossi X-Ray T iming Explorer ASM), and hard X-ray (Compton Gamma Ray Observatory BATSE) observations of a 1998 outburst in the recurring X-ray transient 4U 1630[47, where radio emission was detected for the Ðrst time. The radio observations identify the position of 4U 1630[47 to within 1A. Because the radio emission is optically thin with a spectral index of D[0.8 during the rise, peak, and decay of the initial radio event, the emission is probably coming from an optically thin radio jet ejected over a period of time.