出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We have carried out multi-frequency radio observation of the microquasar Cygnus X-3 during
2006 May-June, when Cygnus X-3 underwent one of the largest flare in its recorded history. We
used the Giant Metrewave Radio Telescope (GMRT) at 244 and 614 MHz. We have also used
archival Very Large Array (VLA) data at 8.43 and 43.3 GHz. Using these measurements and
also using the published results from RATAN, we construct the radio spectrum during both rising
and fading phases of the flare. The radio spectrum clearly shows the turn-over frequency shifting
towards lower radio frequencies as the flare evolves. The two point spectral index from the simultaneous
observations at 244 and 614 MHz shows clear variation from positive (optically thick)
and negative (optically thin) values, which is consistent with the synchrotron self absorption. Applying
the synchrotron self absorption model, we obtain the physical parameters such as the size
of the emitting region, turn over frequency and corresponding peak flux. By obtaining the size of
the emitting region at different epochs of the flare, we estimate the velocity of the expansion of
the blob to be in the range 0.04c to 0.34c, assuming the magnetic field strength in the range 0.1 to
1 Gauss. This is in broad agreement with the known expansion velocities of other micro-quasars.
