X-ray flares from the stellar tidal disruption by a candidate supermassive black hole binary

TL;DR

This paper reports the discovery of delayed X-ray brightening in a tidal disruption event, suggesting the possible presence of a supermassive black hole binary or obscuration effects, highlighting the importance of X-ray observations in understanding TDEs.

Contribution

It presents the first detection of delayed X-ray brightening in a TDE, proposing a new scenario involving black hole binaries or obscuration affecting early X-ray emission.

Findings

Delayed X-ray brightening observed 140 days after optical outburst

Flux dips during decay phase suggest complex obscuration or binary interactions

X-ray observations can reveal supermassive black hole binaries in TDEs

Abstract

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.