Precursors in tidal disruption events: repeating, fast, and AGN-hosted TDEs

TL;DR

This study compiles and analyzes precursor features in tidal disruption events, revealing their association with specific TDE subclasses and suggesting their origin from debris-disk interactions, which enhances understanding of TDE optical emissions.

Contribution

First comprehensive sample of precursor TDEs, identifying their prevalence in certain subclasses and proposing a physical origin related to debris interactions.

Findings

Precursor TDEs mainly occur in repeating, fast, and AGN-hosted TDEs.

Positive correlation between precursor timing and black hole mass.

Precursor features may indicate partial TDEs and debris-disk interactions.

Abstract

Context. Tidal disruption events (TDEs) are rare transients that provide important insights into the physics of galactic nuclei. A recently identified feature in their optical light curves is the presence of early bump-like structures (precursors) that appear before the onset of the main flare or during its rise. Aims. We aim to build and study the first sample of precursor TDEs in order to improve our understanding of these features, which could be key to revealing the origin of the optical emission in TDEs. Methods. We compiled all known precursor TDEs from the literature, searched for additional candidates, and analyzed them as a sample. Results. We find that precursor TDEs predominantly fall within the repeating TDE, fast TDE, and TDE in active galactic nucleus (AGN) subclasses. We reveal a positive correlation between the occurrence time of the precursors relative to the main peak and the central black hole mass. Conclusions. We suggest that the precursors appear due to interactions between the incoming stellar debris and the disk or leftover material from an earlier disruption (repeating and fast TDEs) or a stable pre-existing disk (TDEs in AGNs). Precursors are therefore potentially key signatures of repeating partial TDEs in previously quiescent galaxies.