Letter to the Editor

Hints for a fast precessing relativistic radio jet in LS I +61°303

¹ Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: mmassi@mpifr-bonn.mpg.de
² Service d'Astrophysique, CEA Saclay, Bât. 709, L'Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France e-mail: mribo@discovery.saclay.cea.fr
³ Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain e-mail: jmparedes@ub.edu
⁴ Nuffield Radio Astronomy Laboratories, Jodrell Bank, Macclesfield, Cheshire SK11 9DL, UK e-mail: stg@jb.man.ac.uk
⁵ Institut d'Informática i Aplicacions, Universitat de Girona, Campus de Montilivi s/n, 17071 Girona, Spain e-mail: marta.peracaula@udg.es
⁶ Departamento de Física, Escuela Politécnica Superior, Univ. de Jaén, Virgen de la Cabeza 2, 23071 Jaén, Spain e-mail: jmarti@ujaen.es

Corresponding author: M. Massi, mmassi@mpifr-bonn.mpg.de

Received: 31 July 2003
Accepted: 5 December 2003

Abstract

Here we discuss two consecutive MERLIN observations of the X-ray binary LS I +61°303. The first observation shows a double-sided jet extending up to about 200 AU on both sides of a central source. The jet shows a bent S-shaped structure similar to the one displayed by the well-known precessing jet of SS 433. The precession suggested in the first MERLIN image becomes evident in the second one, showing a one-sided bent jet significantly rotated with respect to the jet of the day before. We conclude that the derived precession of the relativistic () jet explains puzzling previous VLBI results. Moreover, the fact that the precession is fast could be the explanation of the never understood short term (days) variability of the associated gamma-ray source 2CG 135+01/3EG J0241+6103.