EDP Sciences
Free access
Issue
A&A
Volume 414, Number 1, January IV 2004
Page(s) L1 - L4
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20031760


A&A 414, L1-L4 (2004)
DOI: 10.1051/0004-6361:20031760

Letter

Hints for a fast precessing relativistic radio jet in LS I +61 $^{\circ}$303

M. Massi1, M. Ribó2, J. M. Paredes3, S. T. Garrington4, M. Peracaula5 and J. Martí6

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

(Received 31 July 2003 / Accepted 5 December 2003)

Abstract
Here we discuss two consecutive MERLIN observations of the X-ray binary LS I +61 $^{\circ}$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 ( $\beta=0.6$) 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 .


Key words: stars: individual: LS I +61 $^{\circ}$303 , 2CG 135+01 , 3EG J0241+6103 -- X-rays: binaries -- radio continuum: stars -- gamma-rays: observations -- gamma-rays: theory

Offprint request: M. Massi, mmassi@mpifr-bonn.mpg.de

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