Letter to the Editor

Recurrent microblazar activity in Cygnus X-1?

¹ Instituto Argentino de Radioastronomía, C.C.5, (1894) Villa Elisa, Buenos Aires, Argentina
² CEA/DMS/DAPNIA/Service d'Astrophysique, Centre d'Études de Saclay, 91191 Gif-sur-Yvette, France
³ Instituto de Astronomía y Física del Espacio/CONICET, C.C. 67, Suc. 28, Buenos Aires, Argentina

Corresponding author: G. E. Romero, romero@venus.fisica.unlp.edu.ar

Received: 11 July 2002
Accepted: 20 August 2002

Abstract

Recurrent flaring events at X- and soft gamma-ray energies have been recently reported for the galactic black hole candidate Cygnus X-1. The observed fluxes during these transient outbursts are far higher than what is observed in “normal” episodes. Here we suggest that the origin of this radiation is non-thermal and produced by inverse Compton interactions between relativistic electrons in the jet and external photon fields, with a dominant contribution from the companion star field. The recurrent and relatively rapid variability could be explained by the precession of the jet, which results in a variable Doppler amplification.