An Untargeted Search for Radio-Emitting Tidal Disruption Events in the VAST Pilot Survey

TL;DR

This paper reports a systematic radio survey for tidal disruption events (TDEs) using ASKAP data, identifying 12 candidates and estimating their volumetric rate, providing new insights into TDE occurrence in the radio regime.

Contribution

First systematic search for radio TDEs in the VAST survey, identifying candidates and estimating their volumetric rate, expanding understanding of TDEs in radio wavelengths.

Findings

Identified 12 candidate radio TDEs with durations 6-230 days.

Estimated jetted TDE rate of 0.80 Gpc$^{-3}$ yr$^{-1}$.

Radio TDE properties consistent with relativistic jet models.

Abstract

We present a systematic search for tidal disruption events (TDEs) using radio data from the Variables and Slow Transients (VAST) Pilot Survey conducted using the Australian Square Kilometre Array Pathfinder (ASKAP). Historically, TDEs have been identified using observations at X-ray, optical, and ultraviolet wavelengths. After discovery, a few dozen TDEs have been shown to have radio counterparts through follow-up observations. With systematic time-domain radio surveys becoming available, we can now identify new TDEs in the radio regime. A population of radio-discovered TDEs has the potential to provide several key insights including an independent constraint on their volumetric rate. We conducted a search to select variable radio sources with a single prominent radio flare and a position consistent within 2$\sigma$ of the nucleus of a known galaxy. While TDEs were the primary target of our search, sources identified in this search may also be consistent with active galactic nuclei exhibiting unusual flux density changes at the timescales probed, uncharacteristically bright supernovae, or a population of gamma-ray bursts. We identify a sample of 12 radio-bright candidate TDEs. The timescales and luminosities range from ~6 to 230 days and ~10$^{38}$ to 10$^{41}$ erg s$^{-1}$, consistent with models of radio emission from TDEs that launch relativistic jets. After calculating the detection efficiency of our search using a Monte Carlo simulation of TDEs, and assuming all 12 sources are jetted TDEs, we derive a volumetric rate for jetted TDEs of 0.80$^{+0.31}_{-0.23}$ Gpc$^{-3}$ yr$^{-1}$, consistent with previous empirically estimated rates.