  We present a partial analysis of a multi-wavelength study of the X-ray binary
Cir X-1, a system harboring the most relativistic outflow in our galaxy so far.
The data were taken (almost) simultaneously in radio and X ray during a survey
carried out in October 2000 and December 2002. Cir X-1 was observed at the
radio frequencies of 4.8 and 8.6 GHz with the Australia Telescope Compact Array
(ATCA). In the X-ray spectral domain we used the Rossi X-Ray Timing Explorer
(RXTE). We found strong evidence for flaring activity in radio not only at the
periastron but also at the apoastron passages. A comparison of our data against
different correlations between radio and X ray found in other neutron star
systems shows that Cir X-1 does not seem to follow the general trend. However,
the fact that Cir X-1 is an `exotic' X-ray binary makes any interpretation more
complicated.
