Late-time observations of a candidate relativistic tidal disruption flare

The exceptional properties of a handful of extremely longlived, SwiftBATdetected flares have marked them as a new class of event, likely, but notuniquely caused by the creation of a relativistic jet during the tidaldisruption of star. Here we propose to obtain a further observation of by farthe best studied event, Swift J1644+57, 6 years after the initial outburst.Swift J1644+57 displayed a sharp cutoff in its Xray emission approximately 500days post trigger and has since plateaued at a level a factor >100 lower thanbefore the drop. Our observations will determine if this emission is caused by acontinuation of transient emission after the switchoff of a relativistic jet,or if it is due to the presence of an AGN in the host galaxy. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]