Thermal electrons in the radio afterglow of relativistic tidal disruption event ZTF22aaajecp/AT2022cmc

TL;DR

This study presents long-term radio and sub-millimeter observations of the relativistic TDE AT2022cmc, revealing a spherical outflow with thermal electrons and providing new insights into jet microphysics.

Contribution

It introduces the first inference of thermal electron populations in a jetted transient, enhancing understanding of relativistic jet microphysics.

Findings

Best fit by a relativistic spherical outflow with R^-1.8 density profile

AT2022cmc is twice as energetic as Swift J1644

Detection of thermal electrons in a jetted TDE

Abstract

A tidal disruption event (TDE) occurs when a star travels too close to a supermassive black hole. In some cases, accretion of the disrupted material onto the black hole launches a relativistic jet. In this paper, we present a long term observing campaign to study the radio and sub-millimeter emission associated with the fifth jetted/relativistic TDE: AT2022cmc. Our campaign reveals a long lived counterpart. We fit three different models to our data: a non-thermal jet, a spherical outflow consisting of both thermal and non-thermal electrons, and a jet with thermal and non-thermal electrons. We find that the data is best described by a relativistic spherical outflow propagating into an environment with a density profile following R^-1.8. Comparison of AT2022cmc to other TDEs finds agreement in the density profile of the environment but also that AT2022cmc is twice as energetic as the other well-studied relativistic TDE Swift J1644. Our observations of AT2022cmc allow a thermal electron population to be inferred for the first time in a jetted transient providing, new insights into the microphysics of relativistic transients jets.