VLBA observations of the superluminal radio jet from Cygnus X-I in the low/hard X-ray state

We present the detection of a resolved jet-like radio-emitting structure fr om the blackhole candidate and X-ray binary source Cygnus X-1 at both 8.4 G Hz and 15 GHz. The structure in the milli-arcsecond resolution observation with the VLBA at 15 GHz shows an extended emission region to the north-west and possibly also perpendicular emitting regions, believed to be in the or bital plane. This X-ray state is believed to be associated with an advectiv e accretion environment. These observations were spaced 2 days apart over t he 5.6-day orbital period. The images confirm the existence of persistent e mission from the source front both an unresolved core and a variable, and a t least moderately (> 0.6c) relativistic jet, during the low/hard X-ray sta te. However, at this resolution and wavelength they do not show any sign of the emission in the orbital plane observed at a 5 sigma level at 15 GHz in the initial epoch.