Development of a two-sided relativistic jet in Cygnus X-3

¹ Departamento de Física, Escuela Politécnica Superior, Universidad de Jaén, Virgen de la Cabeza 2, 23071 Jaén, Spain
² Departament d'Astronomia i Meteorologia, Facultat de Física, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain e-mail: josep@am.ub.es, mperacau@am.ub.es

Corresponding author: J. Martí, jmarti@ujaen.es

Received: 4 May 2001
Accepted: 20 June 2001

Abstract

We present multi-epoch radio maps of the microquasar Cygnus X-3 obtained with the Very Large Array (VLA). The observations were carried out as a Target-of-Opportunity (ToO) project triggered by a series of strong (>5 Jy) radio outbursts in September 2000. We find that Cygnus X-3 was well resolved and clearly elongated in the North-South direction at the VLA resolution in the weeks after the triggering events. In particular, the VLA map from our final epoch of observation perfectly shows the development of a two-sided radio jet extending over ~0.05 pc scales. We interpret both the proper motion and the brightness asymmetry between the jet components in the framework of special relativity effects. Assuming a distance of 10 kpc, the true jet velocity that we derive is close to with a large angle with the line of sight. The possible connection between the VLA bipolar jets and the elongated one-sided structures observed at milli-arcsecond angular scales is also discussed.