A new mechanism for soft X-ray excess in NGC 5548

Abstract

Many active galaxies exhibit soft X-ray excess in the 0.2-2 keV band with a photon index $\alpha _\mathrm{s} \sim 2.38 \pm 0.25$, much higher than that of the hard X-ray (2-10 keV) band with $\alpha _\mathrm{h} \sim 1.7$. Different theoretical models have been proposed to reproduce and explain the spectra, but the complexity of all these models tends to make the situation even more confused. Here we present results using our newly-proposed synchro-curvature mechanism, which we show can reproduce the soft X-ray excess by a simple fitting process. Such a model may be helpful in considering the physical processes taking place in these objects.