Synchrotron flaring behaviour of Cygnus X-3 during the February-March 1994 and September 2001 outbursts
Tuorla Observatory, Väisälä Institute of Space Physics and Astronomy, University of Turku, 21500 Piikkiö, Finland e-mail: firstname.lastname@example.org
2 Metsähovi Radio Observatory, Helsinki University of Technology, 02540 Kylmälä, Finland
3 Geneva Observatory, University of Geneva, Ch. des Maillettes 51, 1290 Sauverny, Switzerland
4 INTEGRAL Science Data Centre, Ch. d'Ecogia 16, 1290 Versoix, Switzerland
5 Observatory, PO Box 14, 00014 University of Helsinki, Finland
6 Astrophysics, Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
7 UCD School of Mathematical Sciences, University College Dublin, Belfield, Dublin 4, Ireland
8 Special astrophysical observatory RAS, Nizhnij Arkhyz, 369167, Russia
9 Department of Physics, University of Turku, 20100 Turku, Finland
Accepted: 15 July 2007
Aims.In this paper we study whether the shock-in-jet model, widely used to explain the outbursting behaviour of quasars, can be used to explain the radio flaring behaviour of the microquasar Cygnus X-3.
Methods.We have used a method developed to model the synchrotron outbursts of quasar jets, which decomposes multifrequency lightcurves into a series of outbursts. The method is based on the Marscher & Gear (1985, ApJ, 298, 114) shock model, but we have implemented the modifications to the model suggested by Björnsson & Aslaksen (2000, ApJ, 533, 787), which make the flux density increase in the initial phase less abrupt. We study the average outburst evolution, as well as specific characteristics of individual outbursts and physical jet properties of Cyg X-3.
Results.We find that the lightcurves of the February-March 1994 and September 2001 outbursts can be described with the modified shock model. The average evolution shows that, instead of the expected synchrotron plateau, the flux density is still increasing during the synchrotron stage. We also find that high frequency peaking outbursts are shorter in duration than those peaking at lower frequencies. Finally, we show that the method can be used, complementary to radio interferometric jet imaging, for deriving the physical parameters such as the magnetic field strength and the energy density of relativistic electrons in the jet of Cyg X-3.
Key words: radiation mechanisms: non-thermal / stars: individual: Cygnus X-3 / infrared: stars / radio continuum: stars
© ESO, 2007