2007ApJ...663L..93H

We analyzed the zero-order image of a 50 ks Chandra gratings observation of Circinus X-1, taken in 2005 during the source's low-flux state. Circinus X-1 is an accreting neutron star that exhibits ultrarelativistic arcsecond-scale radio jets and diffuse arcminute-scale radio jets and lobes. The image shows a clear excess along the general direction of the northwestern counterjet, coincident with the radio emission, suggesting that it originates either in the jet itself or in the shock that the jet is driving into its environment. This makes Circinus X-1 the first neutron star for which an extended X-ray jet has been detected. The kinetic jet power that we infer is significantly larger than the minimum power required for the jet to inflate the large-scale radio nebula.