2006ApJ...641..410K

We report on new X-ray observations of the large-scale jets recently discovered in X-rays from the black hole candidate 4U 1755-33. Our observations in 2004 show that the jets found in 2001 are still present in X-rays. However, sensitive radio observations in 2004 failed to detect the jets. We suggest that synchrotron radiation is a viable emission mechanism for the jets and that thermal bremsstrahlung and inverse Compton emission are unlikely on energetic grounds. In the synchrotron interpretation, the production of X-rays requires acceleration of electrons up to ∼60 TeV, the jet power is ∼4x10³⁵ ergs/s, and the radio nondetection requires a spectral index α>-0.65 (S_ν∝ν^α), which is similar to the indexes found in lobes surrounding some other compact objects. We find an upper limit on the flux of 4U 1755-33 in quiescence of 5x10^–16 ergs/cm2/s in the 0.3-8 keV band.