The decay phase of radio flares from GRS1915+105

Abstract

Decays of radio flares from the superluminal galactic source GRS1915+105 are analysed and both exponential and power law decays are fitted to the data. It is found that the exponential law is a marginally better approximation, whereas an expanding plasmon model actually predicts a power law type decay. The reason for this is due to relativistic aberration, time dilation and the Doppler effect, in going from the rest frame of the ejecta to the observer's frame. This effect is relevant for telescopes in which the beamwidth encompasses both approaching and receding plasmons, e.g. the radio monitoring programs at GBI and the Ryle Telescope.