Astrophysicists Detect High-Energy Neutrino from Tidal Disruption Event

The majority of supermassive black holes lie dormant and starved of fuel; these hidden giants can be temporarily illuminated when an unlucky star passes close enough to be tidally disrupted and consumed by the black hole; in some cases, the black hole launches fast-moving particle jets.

A view of the accretion disk around the supermassive black hole, with jet-like structures flowing away from the disk. The extreme mass of the black hole bends spacetime, allowing the far side of the accretion disc to be seen as an image above and below the black hole. Image credit: Science Communication Lab, DESY.

Neutrinos are fundamental particles that far outnumber all the atoms in the Universe but rarely interact with other matter.

Astrophysicists are particularly interested in high-energy neutrinos, which have energies up to 1,000 times greater than those produced by the most powerful particle colliders on Earth.

They think the most extreme events in the Universe, like violent galactic outbursts, accelerate particles to nearly the speed of light. Those particles then collide with light or other particles to generate high-energy neutrinos.

“The origin of cosmic high-energy neutrinos is unknown, primarily because they are notoriously hard to pin down,” said co-lead author Dr. Sjoert van Velzen, a researcher at New York University, the University of Maryland, and Leiden Observatory.

“Our result would be only the second time high-energy neutrinos have been traced back to their source.”

On April 9, 2019, the Zwicky Transient Facility (ZTF), a robotic camera at Caltech’s Palomar Observatory, detected light emitted in a tidal disruption event.

Dubbed AT2019dsg, the event occurred in 2MASX J20570298+1412165, a galaxy located over 690 million light-years away in the constellation of Delphinus.

Then, on Oct. 1, 2019, NSF’s IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station in Antarctica detected a high-energy neutrino called IC191001A and backtracked along its trajectory to a location in the sky.

About seven hours later, ZTF noted that this same patch of sky included AT2019dsg.

“IC191001A smashed into the Antarctic ice with a remarkable energy of more than 100 teraelectronvolts,” said co-author Professor Anna Franckowiak, a researcher at the University of Bochum.

“This is the first neutrino linked to a tidal disruption event, and it brings us valuable evidence,” said co-lead author Robert Stein, a doctoral student at the German Electron-Synchrotron (DESY) and Humboldt University.

“Tidal disruption events are not well understood. The detection of the neutrino points to the existence of a central, powerful engine near the accretion disk, spewing out fast particles.”

“And the combined analysis of data from radio, optical and ultraviolet telescopes gives us additional evidence that the tidal disruption event acts as a gigantic particle accelerator.”

“Discovering neutrinos associated with tidal disruption events is a breakthrough in understanding the origin of the high-energy astrophysical neutrinos identified by the IceCube detector at the South Pole whose sources have so far been elusive,” said co-author Dr. Glennys Farrar, a researcher at New York University.

“The neutrino- tidal disruption event coincidence also sheds light on a decades old problem: the origin of ultrahigh energy cosmic rays.”

“Tidal disruption events are incredibly rare phenomena, only occurring once every 10,000 to 100,000 years in a large galaxy like our own. Astronomers have only observed a few dozen at this point,” said co-author Dr. S. Bradley Cenko, a researcher at NASA’s Goddard Space Flight Center and the University of Maryland.

“Multiwavelength measurements of each event help us learn more about them as a class, so AT2019dsg was of great interest even without an initial neutrino detection.”

“We predicted that neutrinos and tidal disruptions could be related, and seeing that for the first time in the data is just very exciting,” Dr. van Velzen said.

“This is another example of the power of multimessenger astronomy, using a combination of light, particles, and space-time ripples to learn more about the cosmos.”

“The combined observations demonstrate the power of multimessenger astronomy,” said co-lead author Professor Marek Kowalski, a researcher at DESY and Humboldt University.

“Without the detection of the tidal disruption event, the neutrino would be just one of many. And without the neutrino, the observation of the tidal disruption event would be just one of many.”

“Only through the combination could we find the accelerator and learn something new about the processes inside.”

“We might only be seeing the tip of the iceberg here,” said Professor Francis Halzen, a researcher at the University of Wisconsin-Madison and principal investigator of IceCube, who was not directly involved in the study.

“In the future, we expect to find many more associations between high-energy neutrinos and their sources.”

“There is a new generation of telescopes being built that will provide greater sensitivity to tidal disruption events and other prospective neutrino sources. Even more essential is the planned extension of the IceCube neutrino detector, that would increase the number of cosmic neutrino detections at least tenfold.”

The discovery is reported in a paper in the journal Nature Astronomy.A

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