X-ray flares from the stellar tidal disruption by a candidate
  supermassive black hole binary
  Optical transient surveys have led to the discovery of dozens of stellar
tidal disruption events (TDEs) by massive black hole in the centers of
galaxies. Despite extensive searches, X-ray follow-up observations have
produced no or only weak X-ray detections in most of them. Here we report the
discovery of delayed X-ray brightening around 140 days after the optical
outburst in the TDE OGLE16aaa, followed by several flux dips during the decay
phase. These properties are unusual for standard TDEs and could be explained by
the presence of supermassive black hole binary or patchy obscuration. In either
scenario, the X-rays can be produced promptly after the disruption but are
blocked in the early phase, possibly by a radiation-dominated ejecta which
leads to the bulk of optical and ultraviolet emission. Our findings imply that
the reprocessing is important in the TDE early evolution, and X-ray
observations are promising in revealing supermassive black hole binaries.
