2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/5049Multifrequency VLA and OVRO observations of the radio outburst of Cygnus X-3 in September 2001 are presented, illustrating the evolution of the spectrum of the source over a period of six days. An estimate of the magnetic field in the emitting region is made from the spectral turnover and possible explanations for the spectral evolution are suggested.4 pages, 2 figures, to appear in Proceedings of the 4th Microquasar Workshop, eds. Ph Durouchoux, Y. Fuchs and J. RodriguezAstrophysicstext