Radio emission observations reveal delayed outflow from a tidal disruption event
Tomasz Nowakowski
astronomy writer
Sadie Harley
scientific editor
Robert Egan
associate editor
Astronomers have performed radio observations of WTP 14adeqka—a tidal disruption event discovered a decade ago. Results of the observational campaign, August 22 on the pre-print server arXiv, provide crucial insights regarding the radio emission from this source.
Tidal disruption events (TDEs) are phenomena which occur when a star passes close enough to a supermassive black hole and is pulled apart by the black hole's tidal forces, causing the process of disruption. Radio observations of synchrotron emission from TDE ejecta have the potential to reveal the presence and properties of nonrelativistic quasi-spherical outflows, on-axis jets, or off-axis jets.
Recent observations show that many optically-discovered TDEs exhibit radio emission delayed by about two to three years. This puzzling time lag is assumed to be due to off-axis jets, a previously unknown phase of the outflow, a complex density structure surrounding the supermassive black hole (SMBH), or delayed, nonrelativistic outflows.
WTP 14adeqka is a tidal disruption event at a redshift of 0.019, discovered in 2015 with NASA's Wide-field Infrared Survey Explorer (WISE). It was initially identified as a flare, which peaked about two years after the initial detection with a mid-infrared luminosity of about 10 tredecillion erg/s.
Now, a team of astronomers led by Walter W. Golay of the Harvard-Smithsonian Center for Astrophysics (CfA) reports that WTP 14adeqka is one of those TDEs, which exhibits a delayed radio emission. The finding is the result of observations using the Very Large Array (VLA) and the Very Long Baseline Array (VLBA).
"In this paper, we present a detailed radio study of WTP 14adeqka using archival and targeted observations spanning about 4–10 years after disruption, making this event the first mid-infrared TDE with detected delayed radio emission," the scientists wrote.
The observations detected rising radio emission starting approximately four years after the discovery of the mid-infrared emission, peaking about 2.5 years later with a luminosity at a level of 2 duodecillion erg/s, and declining thereafter. The most recent observations, conducted in 2025, show that WTP 14adeqka is still exhibiting bright radio emission.
The study found that the radio outflow from WTP 14adeqka has an energy reaching 500 quindecillion erg, equipartition energy radius of 0.2 light years, and magnetic field strength of 0.12 Gauss. The collected data also indicate a steady peak frequency at 2.0 GHz, with mild fading.
The astronomers noted that the relatively small size of the emission region and the lack of astrometric motion rule out the possibility that the radio emission is from a promptly launched off-axis jet. They added that their study proves that mid-infrared TDEs can launch energetic, delayed outflows.
"Ongoing radio observations of the full mid-infrared TDE sample will reveal whether this behavior is ubiquitous," the authors of the paper conclude.
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More information: Walter W. Golay et al, Radio Emission from the Infrared Tidal Disruption Event WTP14adeqka: The First Directly Resolved Delayed Outflow from a TDE, arXiv (2025).
Journal information: arXiv
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