Near Real-Time Gravitational Wave Data Analysis of the Massive Black Hole Binary with TianQin

Space-borne gravitational wave (GW) detectors can detect the merger ofmassive black holes. The early warning and localization of GW events beforemerging can be used to inform electromagnetic telescopes and conductmultimessenger observations. However, this requires real-time data transmissionand analysis capabilities. The geocentric orbit of the space-borne GW detectorTianQin makes it possible to conduct real-time data transmission. In thisstudy, we develop a search and localization pipeline for massive black holebinaries (MBHBs) with TianQin under both regular and real-time datatransmission modes. We demonstrate that, with real-time data transmission,MBHBs can be accurately localized on the fly. With the approaching merger, eachanalysis can be finished in only 40 min. For an MBHB system at a distance of 1Gpc, if we receive data every hour, then we can pinpoint its location to withinless than 1 deg^2 on the final day before the merger.