Continued Rapid Radio Brightening of the Tidal Disruption Event AT2018hyz

TL;DR

This paper reports ongoing radio brightening of the TDE AT2018hyz over 1370-2160 days, showing a rising light curve consistent with either a delayed spherical outflow or an off-axis relativistic jet, with implications for TDE models.

Contribution

It provides the first long-term radio light curve of AT2018hyz, revealing continued brightening and constraining the nature of its outflow or jet.

Findings

Radio emission continues to rise over 1370-2160 days.

Peak luminosity reaches ~10^40 erg/s, similar to Swift 1644+57.

Data are consistent with either a delayed spherical outflow or an off-axis relativistic jet.

Abstract

We present ongoing radio observations of the tidal disruption event (TDE) AT2018hyz, which was first detected in the radio at 972 days after disruption, following multiple non-detections from earlier searches. The new observations presented here span approximately 1370-2160 days and 0.88-240 GHz. We find that the light curves continue to rise at all frequencies during this time period, following a power law of about F ~ t^3 (compared to F_nu ~ t^5.7 at 972-1400 days), and reaching a peak luminosity of L~ 10^40 erg/s, comparable to the luminosity of the relativistic TDE Swift 1644+57 on the same timescale. The multi-frequency data indicate that the peak frequency does not significantly evolve over the 1030-day span of our observations, while the peak flux density increases by an order of magnitude. The observed behavior is consistent with two possible scenarios: (i) a delayed spherical outflow launched about 620 days post-disruption with a velocity of ~0.3c and an energy of ~10^50 erg, and (ii) a highly off-axis (~80-90 deg) relativistic jet with a Lorentz factor of Gamma ~8 and E_K ~ 10^52 erg. Continued radio observations to capture the light curve peak, as well as VLBI observations, could distinguish between these scenarios.