Rogue black hole shocks astronomers with record radio blast

An international team led by Dr. Itai Sfaradi and Prof. Raffaella Margutti of the University of California, Berkeley, together with collaborators from around the world, including Prof. Assaf Horesh of the Racah Institute of Physics at the Hebrew University of Jerusalem, identified the first TDE to produce bright radio signals away from a galaxy's core.

The event, named AT 2024tvd, exhibited the fastest-changing radio emission ever recorded from a black hole consuming a star.

"This is truly extraordinary," said Dr. Itai Sfaradi, the study's lead author. "Never before have we seen such bright radio emission from a black hole tearing apart a star, away from a galaxy's center, and evolving this fast. It changes how we think about black holes and their behavior."

Dr. Sfaradi, a former student of Prof. Horesh, led the groundbreaking research. "This is one of the fascinating discoveries I've been part of," said Prof. Horesh. "The fact that it was led by my former student, Itai, makes it even more meaningful. It's another scientific achievement that places Israel at the forefront of international astrophysics."

A black hole far from home

A tidal disruption event occurs when a star strays too close to a massive black hole and is pulled apart by its immense gravitational forces.

In this rare instance, the black hole was found roughly 2,600 light-years (0.8 kiloparsecs) from the center of its host galaxy -- strong evidence that supermassive black holes can exist in surprising and previously overlooked locations.

The key role of radio observations

The discovery was made possible through high-quality observations from several of the world's premier radio telescopes, including the Very Large Array (VLA), ALMA, ATA, SMA, and the Arcminute Microkelvin Imager Large Array (AMI-LA) in the UK.

The AMI observations, led by the Hebrew University team, were crucial in revealing the unusually rapid evolution of the radio emission -- a hallmark of this event and a major clue to understanding its physical nature.

The data showed two distinct radio flares evolving faster than any TDE observed before. These results indicate that powerful outflows of material were launched from the vicinity of the black hole not immediately after the stellar destruction, but months later, suggesting delayed and complex processes in the aftermath of the disruption.

Detailed modeling points to at least two separate ejection events, months apart -- clear evidence that black holes can episodically "reawaken" after periods of apparent inactivity.

The research was conducted in collaboration with scientists from institutions across the United States, Europe, and Israel, including Prof. Paz Beniamini of the Open University of Israel, and was published in The Astrophysical Journal Letters.