Discovery of a double radio source associated with Cygnus X-3

Abstract

The combination of high X-ray luminosity1 (∼1038 erg s-1), short orbital period2 (4.8 hours), large non-thermal radio outbursts3-5 and reports of very-high-energy (up to 1015 eV) γ-ray emission6,7 (see also ref. 8) and muon-rich showers9-11 makes Cyg X-3 a unique object among X-ray binaries. Very-high-resolution spatial mapping shows that the radio source starts expanding at the beginning of outbursts and becomes elongated4,5,12, indicating that Cyg X-3 contains a relativistic jet, similar to SS433 (ref. 13). We report here the discovery of a weak (∼4.5 mJy), arcsecond-scale double radio source located symmetrically with respect to the compact variable radio core of Cyg X-3. The double radio source has a separation of about 6 arcsec and is roughly aligned with the elongation direction of the sub-arcsec core from Very-Long-Baseline Interferometry observations12,14,15. Like the latter it has a rather broad opening angle. This suggests a generic connection between the inner and outer radio structures, and implies that the (poor) collimation evident in the large-scale double source originates near the binary system. © 1989 Nature Publishing Group.