Hebrew University finds first evidence of delayed radio flares after star destroyed by black hole

A team of researchers from the Hebrew University of Jerusalem (HUJI) led by dr. Assaf Horesh discovered the first evidence of radio flares just long after a star was destroyed by a black hole. Published in the magazine Natural Astronomy, the discovery was based on ultra-powerful radio telescopes to study these catastrophic cosmic events in distant galaxies called Tidal Disruption Events (TDE). While researchers knew that these events caused the release of radio flares, this latest discovery saw the flares emit months or even years after the stellar disruption. The team was led by dr. Horesh of the Racah Institute of Physics in Hebrew, along with NASA Swift Space Telescope Director, Professor Brad Cenko, and dr. Iair Arcavi of Tel Aviv University.

“According to existing theories about how these events occur, there is no expectation that a radio would be discovered later in the immediate aftermath of the disruption,” says Dr Horesh. “However, we decided to conduct a last radio observation six months after the star was destroyed, and surprisingly, we discovered a clear radio emission. data collection continued, during which the radio emission attenuated.In addition, we found a second delayed flare, four years after the initial discovery of stellar disruption.This is the first discovery of such delayed radio flares of such events, when a star by a black hole is disrupted. ‘

Flares are believed to be caused by a large velocity jet that is launched when the star is destroyed and sucked into the black hole or due to the external explosion of debris from the explosion.

The analysis of the delayed radio flares leads the research team to various conclusions.

First, they now believe that new models need to be developed to explain such a long delay in the emission of radio flares. Secondly, it is possible that such delayed radio flares are a common phenomenon, but to find more of them, teams will have to stay focused on observations around the areas concerned long after the initial disruption. Third, it is possible that a significant amount of stellar matter eventually folds into the black hole (is retracted), but only long after the star has been destroyed.

“What led to the delay and what is the exact physical process responsible for such late emissions are still open questions,” says Dr Horesh. “In light of this discovery, we are actively seeking more such delayed radio flares in other tidal disruption events.”

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