The Hebrew University finds the first evidence of delayed radio flames after the star was destroyed by a black hole

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

“According to existing theories of how these events take place, there is no expectation that this will happen later if no radio broadcast is detected in the immediate aftermath of the disruption,” said Dr. Horesh. “However, we decided to do one last radio observation six months after the star was destroyed, and surprisingly, we discovered bright radio waves. Once we discovered these delayed radio bursts, we continued to collect data for a year during which the radio emissions faded away. In addition, we found a second delayed solar flare, four years after the first discovery of the perturbation of the stars. This is the first discovery of such delayed radio flares from such events, when a star is perturbed by a black hole. “

Flares are believed to be caused by a high-speed jet launched when the star is destroyed and sucked into the black hole, or as a result of the outward blast of debris from the blast.

The analysis of the delayed radio flames led the research team to several conclusions.

First, they believe that new models need to be developed to explain such a long delay in radio burst transmission. Second, such delayed radio flames may be a common occurrence, but to find more of them, teams will have to continue to focus on observations around affected areas long after the initial disruption. Third, it is possible that a significant amount of the stellar debris will eventually become accented (drawn in) in the black hole, but only long after the star is destroyed.

“What led to the delay and the exact physical process responsible for such late transmissions are still open questions,” said Dr. Horesh. “In light of this discovery, we are actively looking for more such delayed radio flares in other tidal disturbances.”