Probing the behaviour of the X‐ray binary Cygnus X‐3 with very long baseline radio interferometry

In order to test the recently proposed classification of the radio/X-ray states of the X-ray binary Cygnus X-3 (Cyg X-3), we present an analysis of the radio data available for the system at much higher spatial resolutions than used for defining the states. The radio data set consists of archival Very Long Baseline Array data at 5 or 15 GHz and new electronic European Very Long Baseline Interferometry Network data at 5 GHz. We also present 5-GHz Multi-Element Radio Linked Interferometer Network observations of an outburst of Cyg X-3. In the X-ray regime, we use quasi-simultaneous with radio, monitoring and pointed Rossi X-ray Timing Explorer observations. We find that when the radio emission from both jet and core is globally considered, the behaviour of Cyg X-3 at mas scales is consistent with that described at arcsec-scales. However, when the radio emission is disentangled in a core component and a jet component, the situation changes. It becomes clear that in active states the radio emission from the jet is dominating that from the core. This shows that in these states the overall radio flux cannot be used as a direct tracer of the accretion state.