Exploring the Role of Jets in the Radio/X-ray Correlations of GX339-4

摘要

The Galactic black hole candidate X-ray binary GX339-4 spends most of itstime in the low/hard state, making it an ideal candidate for modeling theassumedly low accretion phase. The radio emission correlates very tightly withthe X-rays over more than two orders of magnitude in X-ray flux density,suggesting that the jet plasma also plays a role at higher frequencies. Wecompare the predictions of our jet model, with and without acceleration, tothirteen broadband simultaneous or quasi-simultaneous spectra over thischanging flux history. In addition, we consider a simple standard thin diskwhich transitions to an optically thin accretion flow, in order to account forthe assumedly thermal optical data seen in some observations. A solutionwithout acceleration cannot describe the data without unrealistic energyrequirements. But because of the low disk luminosity, and possibly the assumeddisk geometry, acceleration in the jet is limited only by synchrotron coolingand can extend easily into the X-rays. We present a model which can account forall the broadband spectra included here, by changing only two parameters in thejet model: the input power and the location of the first acceleration zone.However, the model is most sensitive to changes in the jet power, the varyingof which can also account for the slope of the observed radio/X-ray correlationanalytically. At the highest low/hard state luminosities, the synchrotronself-Compton emission from the jet could be detectable with missions such as{\em GLAST}, providing a way to test the extent of the synchrotroncontribution. We conclude that jet synchrotron is a possible way to explain thebroadband features and this correlation, and discuss ways of incorporating thiscomponent into the ``standard'' corona picture.