Going with the Flow: Can the Base of Jets Subsume the Role of Compact Accretion Disk Coronae?

The hard state of X-ray binaries (XRBs) is characterized by a power lawspectrum in the X-ray band, and a flat/inverted radio/IR spectrum associatedwith occasionally imaged compact jets. It has generally been thought that thehard X-rays result from Compton upscattering of thermal accretion disk photonsby a hot, coronal plasma whose properties are inferred via spectral fitting.Interestingly, these properties-especially those from certain magnetized coronamodels-are very similar to the derived plasma conditions at the jet footpoints.Here we explore the question of whether the `corona' and `jet base' are in factrelated, starting by testing the strongest premise that they are synonymous. Insuch models, the radio through the soft X-rays are dominated by synchrotronemission, while the hard X-rays are dominated by inverse Compton at the jetbase - with both disk and synchrotron photons acting as seed photons. Theconditions at the jet base fix the conditions along the rest of the jet, thuscreating a direct link between the X-ray and radio emission. We also add tothis model a simple iron line and convolve the spectrum with neutralreflection. After forward-folding the predicted spectra through the detectorresponse functions, we compare the results to simultaneous radio/X-ray dataobtained from the hard states of the Galactic XRBs GX339-4 and Cygnus X-1.Results from simple Compton corona model fits are also presented forcomparison. We demonstrate that the jet model fits are statistically as good asthe single-component corona model X-ray fits, yet are also able to address thesimultaneous radio data.Comment: Accepted to the Astrophysical Journal. 14 pages, emulateapj.st