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

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. The radio light curves of TDEs with delayed radio flares are modeled 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, making it challenging to distinguish between these scenarios based on radio data alone. To break this degeneracy, we present calculations of detailed multiwavelength spectra from radio to x-ray and very-high-energy gamma-ray bands, including both synchrotron and inverse-Compton processes. Within this framework, the delayed jet model produces x-ray and optical emission detectable at typical TDE distances, in contrast to wind-driven scenarios. Our results highlight how multiwavelength campaigns offer effective means to distinguish between possible outflow mechanisms. We apply our model to AT 2025aarm, which is one of the closest TDEs that has been observed, and show the importance of x-ray observations.

19 pages, 9 figures, 3 tables, PRD, in press