Probing the Sub-Parsec Dust of a Supermassive Black Hole with the Tidal Disruption Event AT 2020mot

TL;DR

This study uses a tidal disruption event to probe the dust environment within 0.1 parsecs of a supermassive black hole, revealing minimal dust coverage and demonstrating the potential of TDEs for studying black hole surroundings.

Contribution

It provides the first evidence of concentric dust rings within 0.1 parsecs of a SMBH using TDE observations, with implications for understanding black hole environments.

Findings

Dust rings within 0.1 parsecs of SMBH inferred from near-infrared echoes

Dust covering factor is ≤ 2%, much lower than in active galactic nuclei

TDEs can effectively probe the dust environment around SMBHs

Abstract

AT 2020mot is a typical UV/optical tidal disruption event (TDE) with no radio or X-ray signatures in a quiescent host. We find an i-band excess and re-brightening along the decline of the light curve which could be due to two consecutive dust echoes from a TDE. We model our observations following van Velzen et al. (2016) and find that the near-infrared light curve can be explained by concentric rings of thin dust within $\sim$0.1 parsecs of a 6e6 M$_{\odot}$ supermassive black hole (SMBH), among the smallest scales at which dust has been inferred near SMBHs. We find dust covering factors of order fc $\leq$ 2%, much lower than found for dusty tori of active galactic nuclei. These results highlight the potential of TDEs for uncovering the environments around black holes when including near-infrared observations in high-cadence transient studies.