A rogue black hole produces a record-breaking radio signal
An international team of astronomers, led by Dr. Itai Sfaradi and Prof. Raffaella Margutti, reported a breakthrough observation: the first tidal disruption event (TDE) to emit bright radio signals far from a galaxy’s core. Named AT 2024tvd, the event showcases the fastest-changing radio emission ever recorded from a black hole devouring a star. This surprising discovery challenges conventional expectations about where TDEs occur and how they evolve.
The discovery and its significance
Traditionally, TDEs—dramatic occurrences when a star ventures too close to a supermassive black hole—are associated with active galactic centers. AT 2024tvd broke that mold by revealing intense radio activity at a location about 2,600 light-years (0.8 kiloparsecs) from the galaxy’s center. This finding expands our understanding of black holes that may reside in less obvious, quiescent environments and suggests a broader population of off-nuclear TDEs than previously recognized.
The role of radio observations
The discovery was made possible by the world’s premier radio observatories, including the Very Large Array (VLA), ALMA, the Atacama Telescope (ATA), the Submillimeter Array (SMA), and the Arcminute MicroKelvin Imager Large Array (AMI-LA) in the United Kingdom. The AMI-LA observations, led by researchers at the Hebrew University of Jerusalem, were pivotal in capturing the unusually rapid evolution of the radio emission—the key signature that distinguished AT 2024tvd from other TDEs.
Two rapid radio flares and a two-stage outflow
Data reveal two distinct radio flares that evolved faster than any previous TDE. Researchers interpret this as evidence for at least two separate ejection events of material from the region surrounding the black hole. The timing—months apart—implies that the aftermath of stellar disruption can involve delayed, episodic outflows rather than a single, immediate burst.
Implications for black hole physics
The observations suggest that black holes can reawaken after periods of apparent inactivity, launching powerful jets or winds well after the initial disruption. This challenges simple models of TDEs and calls for revised theories on how accretion processes and jet production unfold in off-nuclear environments. The case of AT 2024tvd hints at a more complex interaction between the black hole, the shredded stellar debris, and the surrounding medium than previously imagined.
Global collaboration and the Israeli contribution
The study represents a collaboration across the United States, Europe, and Israel, highlighting the international nature of modern astrophysics. Notably, Prof. Assaf Horesh of the Racah Institute of Physics (Hebrew University of Jerusalem) contributed to the AMI-LA observations, and Dr. Sfaradi, a former student of Prof. Horesh, led the data analysis that unlocked the event’s rapid radio evolution. The work, which also included researchers from the Open University of Israel and institutions across the U.S. and Europe, was published in The Astrophysical Journal Letters.
What comes next
As radio facilities continue to monitor the sky with greater precision across time, more off-nuclear TDEs may be uncovered. These discoveries will refine models of black hole growth, jet formation, and the demographics of black holes in diverse galactic environments. AT 2024tvd stands as a landmark reminder that the cosmos still holds surprises about where and how supermassive black holes interact with their surroundings.
