Blob Ejection from Advection-dominated Accretion Flow II: the Multiwavelength Properties of Light Curves

Abstract

It has been argued that blobs ejected from advection-dominated accretion flow through the accretion-ejection instability undergo expansion due to their high internal energy density. The expanding blobs interact with their surroundings and form strong shock, which accelerates a group of electrons to be relativistic. Then flares are formed. This model has advances in two aspects: shock acceleration and self-consistent injection. We derive an analytical formula of the injection function of relativistic electrons based on the Sedov's law. We calculate the time-dependent spectrum of relativistic electrons in such an expanding blob. The light-travel effect, the evolution of the electron spectrum due to energy loss, and the escape of relativistic electrons from the radiating region are considered, as well as the expansion (at sub-relativistic speed) of the coasting blob. A large number of light curves spanning wide spaces of parameters have been given in this paper. Regarding the symmetry, relative amplitude, duration of a flare, and the time lag between peak fluxes, we find four basic kinds of light curves for the non-expanding blob, and seven basic kinds of light curves for the expanding blob. We also calculate the evolution of the photon spectrum from both non-expanding and expanding blobs. Different shapes in the phase of decreasing luminosity are then obtained for different parameter values. The photon index, $α_{\rm ph}$, keeps constant for non-expanding blobs when luminosity decreases, whereas $α_{\rm ph}$ continues to decrease after the luminosity reaches its maximum for expanding blobs. It is expected that we can extract the information of ejected blobs from the observed light curves based on the present model.