A Newly Discovered Highly Variable IDV Source

Abstract

Short time scale radio variations of compact extragalactic radio quasars and blazars known as IntraDay Variability (IDV) can be explained in at least some sources as a propagation effect; the variations are interpreted as scintillation of radio waves in the turbulent interstellar medium of the Milky Way. One of the most convincing observational arguments in favour of a propagationinduced variability scenario is the observed annual modulation in the characteristic variability time scale due to the Earth's orbital motion. So far there are only two sources known with a well-constrained seasonal cycle. J1128+592 is a recently discovered, highly variable IDV source. Previous, densely time-sampled flux-density measurements with the Effelsberg 100-m radio telescope (Germany) and the Urumqi 25-m radio telescope (China), strongly indicate an annual modulation of the time scale. Here, we summarise the annual modulation model derived using all the measurements, carried out in the last 2.5 years.