New research suggests that a high-energy neutrino can be traced back to a violent encounter of a black hole with a star. However, this origin story is not the only one.
Analysing radio waves from the encounter (AT2019dsg) has revealed that they were quite ordinary, at most as far as a blackhole tearing apart a star is concerned. This means that the neutrino was not produced by the event, and that it wasn't enough energetic to do so months later.
According to Kate Alexander, an astronomer at Northwestern University, "Instead seeing the bright jets of material required for this we see a fainter Radio Outflow of material." We see a soft wind instead of a firehose.
A black hole can cause the death of a star. It's not a simple process. An errant star can get too close to a blackhole to be snared by its gravity. The massive tidal force from the black hole's gravitational field stretches the star and then pulls it so hard it tears it apart.
This is known as a Tidal Disruption Event (TDE). It emits a bright flare of light that glows brightly as half the debris from the star's disintegration swirls around in a disc around the black holes. This generates immense heat and light which is then pulled inexorably beyond its event horizon. The rest of the debris is thrown out into space.
AT2019dsg was the first to be detected from a galaxy approximately 750 million light years away. A supermassive blackhole with a mass 30 million times that of the Sun was confirmed by radio and X-ray observations. Six months later, a neutrino named IC191001A, was detected at Antarctica's IceCube neutrino detector. It had an incredible energy level of more than 200 teraelectronvolts.
Neutrinos are known as "ghost particles" because they have a mass of almost zero and travel at almost light speed. They don't interact with normal matter, so to a neutrino the Universe would seem all but inelastic. However, occasionally they interact and that is how IceCube operates. A neutrino can interact with Antarctic ice to create a flashes of light. These flashes stand out because detectors are buried deep beneath the ice.
Scientists can determine the energy level and direction of the neutrino by studying the light's propagation and brightness. Scientists calculated that IC191001A was derived from AT2019dsg. This is so close that there was only a 0.2 percent chance of the neutrino being unrelated.
Nevertheless, there were some important issues.
"If this neutrino somehow originated from AT2019dsg it raises the question: Why hasn't anyone spotted supernovae associated with neutrinos at this distance or nearer?" Harvard & Smithsonian.
They are more common and have similar energy velocities.
The research team, led by Cendes, used the Atacama Large Millimeter/submillimeter Array in Chile to observe AT2019dsg for over 500 days in radio wavelengths. The researchers found that the TDE continued brightening in radio wavelengths for approximately 200 days before it began to dimming.
The total energy released by the TDE outflow was also calculated. It was approximately the same amount as the Sun's 30 million-year-old energy. This is a pretty standard TDE as well as type Ib or type Ic supernovae.
To produce a neutrino that is as energetic as IC191001A's, the energy of the outflow must have been approximately 1,000 times greater.
It would also have to have had a bizarre geometry, which AT2019dsg did not. At2019dsg is actually quite ordinary. A new explanation may be necessary, since IC191001A does not appear to be an ordinary case.
However, there are still many things we don't know about neutrinos and TDEs. This means that AT2019dsg will continue to be of interest.
Cendes stated, "We're probably going back to check on this one again." "This particular black hole continues to feed."
The Astrophysical Journal published the research.
