Ss433: Outflows Here and There

We summarize the results of VLBA and global VLBI observations of SS433 between 1995 and 2000. With these observations we resolve the inner jet of the source and identify an absorption region (∼ 25 AU), the " central radio gap ". The radio gap is caused by free-free absorption of the jet radio emission by a flattened outflow from the binary system. Radio emission is detected on 100 AU scales perpendicular to the normal jets (" equatorial emission region " ; " equatorial outflow "). At some epochs the emission is smooth but compact features are frequently detected. We suggest that equatorial outflows may be common in microquasars. 1. The radio inner jets The radio inner jets resemble those in AGN in that the jet length is roughly inversely proportional to the frequency, and a " core-shift " is observed between 1.6 and 5 GHz — indicative of self-absorption [1]. The differences are that the SS433 jet is ballistic, it contains protons, and a large fraction of the jet material is probably thermal. The approaching and receding jet sides are separated by a radio gap, as was predicted by Stirling, Spencer & Watson [2]. This is caused by free-free absorption due to a disk-like outflow from the central binary system. The brightness ratio of the two jet sides increases with frequency, and at 22 GHz the receding jet is almost completely absorbed (Fig. 1). The frequency dependence of the size of the mas-scale jet is demonstrated in Fig. 2. The Gaussian FWHM of the main jet feature on the approaching jet side is proportional to ν −0.93 at an epoch when the inner jets were detected up to 22 GHz. The apparent brightness temperature does not show a strong frequency dependence; it is ∼10 9 K on the approaching, and ∼10 8 K on the receding jet side. At 1.6 GHz the brightness ratio reflects only the Doppler-boosting effect and there seems to be no significant free-free absorption on scales larger than ∼50 AU (assuming a distance of 5 kpc). During large flares the inner jet region might disappear, and pairs of plasmons are ejected from the system. There is indication for ongoing electron acceleration in these jet components (Paragi, Stirling & Fejes, these proceedings). 2 Paragi et al. (natural weighting). Contour levels increase by a factor of square root 2, the lowest contour is ±1% of the peak brightness …