Flaring and quiescent radio emission of UX ARIETIS - A time-dependent model

Abstract

Two different interpretations of the quiescent radio emission of UX Ari are considered and compared with available observations. It is assumed that the radiation mechanism is gyrosynchrotron and that the emitting electrons are distributed according to a Maxwellian distribution at the same temperature deduced from X-ray observations and a power-law distribution with different exponents. Both electron populations can reproduce the observed spectrum provided that a suitable configuration of the magnetic field is assumed. The time evolution of a population of electrons following an initial power-law distribution is also studied. It is shown that the spectrum of the emitted radiation evolves, in a time scale of a few days, from the typical spectrum of the flaring emission to the flat one observed in quiescent periods. It is also shown that the intensity distribution reproduces the core-halo structure observed by Mutel et al. (1985) using VLBI for a period of about 1 day after the flare.