Revisiting the infrared/X-ray correlation of GX 339-4 based on a jet model

Abstract

The infrared (IR)/X-ray correlation of GX 339$-$4 is investigated based on a jet model with a modification by linking the magnetic field at the jet base to the accretion rate of the inner accretion flow though the the equilibrium between magnetic pressure at horizon and the ram pressure of the accretion flow. The IR flux is attributed to the synchrotron radiation of the jet, and the X-ray flux is attributed to the advective dominated accretion flow (ADAF), synchrotron radiation of the jet and synchrotron self-Compton scattering (SSC) of the jet, respectively. We find that the observed IR/X-ray correlation with a break is well reproduced with the variation of the accretion rate if the X-ray flux originates from SSC of the jet. Either a conical ballistic jet with the magnetic field parallel to the jet axis or a conical adiabatic jet with an isotropic field can account for the correlation. The power-law index of the energy distribution of electrons $p\sim3$, the minimum Lorentz factor of the electrons $\gamma_{\rm min}\sim60$, the magnetic field $B_0\sim10^5\ {\rm G}$ and the jet radius $R_0\sim10^{10}\ {\rm cm}$ at the jet base are required for both the ballistic jet and the adiabatic jet. This study helps us clarify the complex interaction between the accretion and jet in GX 339$-$4, as well as the properties and geometric structure of the jet, laying the groundwork for exploring similar astrophysical systems.