出版社:SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要:We have observed the micro-quasar V4641 Sgr (SAX J1819.3-2525) at the time of are during
May 2002, using the Giant Metrewave Radio Telescope at low radio frequencies (244 and 610
MHz). This is the lowest frequency radio detection of the source. The source showed clear
signature of spectral evolution from optically thick to thin state. We model the spectral evolution
of the source to obtain some of the source parameters. Assuming the value of magnetic eld
strength to be in the range of 0.1 to 1 Gauss, we obtain the initial velocity of expansion of the jet
to be in the range 0.45c to 0.25c. This is consistent with the known expansion velocities of the
jet with other microquasars.