The 1997 hard state outburst of the X-ray transient GS 1354-64/BW Cir

We present observations of the 1997 outburst of the X-ray transient GS 1354 -64 (BW Cir) at X-ray, optical and, for the first time, radio wavelengths. The X-ray outburst was unusual in that the source remained in the low/hard X-ray state throughout; the X-ray peak was also preceded by at least one op tical outburst, suggesting that it was an 'outside-in' outburst-similar to those observed in dwarf novae systems, although possibly taking place on a viscous timescale in this case. It therefore indicates that the optical emi ssion was not dominated by the reprocessing of X-rays but that instead we s ee the instability directly. White the radio source was too faint to detect any extended structure, spectral analysis of the radio data and a comparis on with other similar systems suggests that mass ejections, probably in the form of a jet, took place and that the emitted synchrotron spectrum may ha ve extended as far as infrared wavelengths. Finally, we compare this 1997 o utburst of GS 1354-64 with possible previous outbursts and also with other hard state objects. both transient and persistent. It appears that a set of characteristics-such as a weak, flat spectrum radio jet, a mHz QPO increas ing in frequency, a surprisingly high optical:X-ray luminosity ratio and th e observed optical peak preceding the X-ray peak-may be common to all hard state X-ray transients.