Interpreting the diversity of afterglow emission from radio-detected tidal disruption events with instantaneous and delayed outflows

TL;DR

This paper models radio light curves of tidal disruption events with delayed outflows, demonstrating that delayed wind models best explain late-time radio flares and can be distinguished from jets through multiwavelength observations.

Contribution

It introduces and compares models of instantaneous, delayed winds, and jets to explain late radio flares in TDEs, emphasizing the importance of delayed outflows.

Findings

Delayed wind models explain late radio flares effectively.

Instantaneous wind models cannot reproduce delayed radio flares.

Delayed jet models produce detectable X-ray and optical emissions.

Abstract

Tidal disruption events (TDEs) occur when a star is gravitationally disrupted by the tidal field of a supermassive black hole during a close encounter. Radio emission has recently been detected in TDEs and is commonly attributed to synchrotron radiation from both wind and jetted outflows. However, several TDEs exhibit bright radio flares at late times, which cannot be easily explained if the wind is launched promptly after the stellar disruption. In this study, we model the radio light curves of TDEs with delayed radio flares using three scenarios: an instantaneous wind, a delayed wind, and a delayed relativistic jet. We show that the instantaneous wind model struggles to reproduce delayed radio flare events, indicating the necessity of an additional delayed outflow component. In contrast, the delayed wind model provides a consistent explanation for the observed radio phenomenology, successfully reproducing events both with and without delayed radio flares. For some delayed radio flare events (e.g., ASASSN-15oi and AT 2019dsg), both the delayed wind and delayed jet models can reproduce the observed radio light curves. The delayed jet model produces x-ray and optical emission that is detectable at typical TDE distances, in contrast to wind-driven scenarios. This highlights how multiwavelength observations offer an effective means of distinguishing among possible outflow mechanisms.