The microarcsecond quasar J1819+3845: Polarization observations and detailed lightcurve analysis

The quasar J1819+3845 shows exceedingly rapid variations in both total inte nsity and linear polarization. These are attributed to interstellar scintil lation. The source contains at least two structural components each of whic h shows variable polarization behaviour. The polarization variations are ge nerally, but perhaps not always, coherent over the 80 MHz band setting. The 6 cm lightcurves in the first few months of 2000 hint at a time-asymmetric behaviour as could be expected from an asymmetric source structure.