Monitoring the microarcsecond quasar J1819+3845

We present the results of a year-long monitoring campaign on J1819+3845. We interpret the results of this WSRT campaign to infer critical source param eters such as source lifetime and structure on tens of microarcseconds. The long lifetime of the source at such high brightness temperatures requires continuous energy injection or exotic emission processes. We have previousl y interpreted the extreme scintillation of J1819+3845 as due to a relativel y nearby (similar to 20 pc) scattering screen. We show this screen has a ve locity w.r.t. the LSR of similar to 25 km s(-1), as measured by the changin g scintillation properties throughout the year: the 'velocity parallax'.