Distinguishing Tidal Disruption Events from Impostors

TL;DR

This paper reviews the challenges in accurately identifying tidal disruption events (TDEs) among various astrophysical transients and proposes using multiple observables for reliable classification.

Contribution

It provides a comprehensive review of TDE characteristics, compares them with impostors, and suggests a multi-observable approach for improved TDE identification.

Findings

Multiple observables are necessary to classify TDEs reliably.

Certain host galaxy and SMBH features statistically distinguish TDEs from non-TDEs.

TDE candidates show distinct population characteristics based on host properties.

Abstract

Recent claimed detections of tidal disruption events (TDEs) in multi-wavelength data have opened potential new windows into the evolution and properties of otherwise dormant supermassive black holes (SMBHs) in the centres of galaxies. At present, there are several dozen TDE candidates, which share some properties and differ in others. The range in properties is broad enough to overlap other transient types, such as active galactic nuclei (AGN) and supernovae (SNe), which can make TDE classification ambiguous. A further complication is that "TDE signatures" have not been uniformly observed to similar sensitivities or even targeted across all candidates. This chapter reviews those events that are unusual relative to other TDEs, including the possibility of TDEs in pre-existing AGN, and summarises those characteristics thought to best distinguish TDEs from continuously accreting AGN, strongly flaring AGN, SNe, and Gamma-Ray Bursts (GRBs), as well as other potential impostors like stellar collisions, "micro-TDEs," and circumbinary accretion flows. We conclude that multiple observables should be used to classify any one event as a TDE. We also consider the TDE candidate population as a whole, which, for certain host galaxy or SMBH characteristics, is distinguishable statistically from non-TDEs, suggesting that at least some TDE candidates do in fact arise from SMBH-disrupted stars.