X-Ray Spectra from Weakly Magnetized Accretion Flows

In this paper, we expand upon previous work that argued for the possibility of a subequipartition magnetic field in the accretion flow of a black hole binary system. Using X-ray observations of the three well-known sources A0620-00, XTE J1118+480, and V404 Cyg during the quiescent state, we compare the theoretically expected spectral shape with the observed data in order to verify that the parameters of the subequipartition model are plausible. In all three cases, we find that it is possible to reproduce the spectral shape of the X-ray observations with a subequipartition flow. These findings support the idea that the quiescent state spectrum of X-ray binary systems is produced by a weakly magnetized accretion flow. A subequipartition flow would pose a significant challenge to our current understanding of jet launching, which relies on the presence of a strong magnetic field to power the jet.