Researchers Identify Origin of Violent Gamma-Ray Outbursts

Super-powerful jets of highly-energetic material dubbed blazars or quasars (depending on our orientation) blast out from supermassive black holes. However, where most of the energy originates has long been a mystery. Researchers have identified the origin of these intense bursts. They appear to come from the center of the blazars of supermassive black holes. The research was led by Lars Fuhrmann of the Max Planck Institute for Radio Astronomy and the results were published in Monthly Notices of the Royal Astronomical Society.

As matter is spiraling around and getting pulled in to a supermassive black hole forming the accretion disk, magnetic forces at the center begin expelling some of the gas away in powerful jets so forcefully, they near the speed of light. Within these jets, high energy gamma-rays are also found, which are the most energetic form of light. Long gamma ray bursts are so energetic, in one second they produce more energy than hundreds of stars like our Sun could produce in 10 billion years combined. 

There have been a few different areas that astronomers suspected were producing these intense gamma-rays. While they could have spawned from the middle of the black hole’s accretion disk, they may have also started from the jets themselves. The astronomers studied about 60 highly-energetic galaxies and utilized radio observations on 11 frequency bands with many telescopes, including NASA’s Fermi Gamma-ray Space Telescope.

“Since the era of the EGRET instrument on the Compton Gamma-ray Observatory in the 1990s, it has been discussed whether outbursts of radio emission are physically connected to similar events occurring at gamma rays,” says co-author Anton Zensus in a press release. “Now with the combination of F-GAMMA radio and Fermi gamma-ray long-term data, and thanks to special analysis techniques, we finally know it!”

Along with Fermi, the researchers used Effelsberg 100-m, IRAM 30-m and APEX 12-m; part of the Fermi-GST AGN Multi-frequency Monitoring Alliance (F-GAMMA) program, which allowed them to use all of the equipment in concert to study the frequency bands. A novel method for statistical analysis was also used in processing the signals, which measured the difference in timing between gamma-rays and other radio signals stemming from the jets. The gamma-rays reached the equipment about 10-80 days sooner than the radio signals.

“For the first time we see that the radio delays become smoothly smaller towards higher radio frequencies,” said co-author Emmanouil Angelakis. “This tells us that the gamma-ray photons are coming from the innermost radio emitting jet regions.”

This information also allowed them to pinpoint where in the jet the gamma-rays originated. “We are talking about only a few light year distances – very close to the footpoint of the jet and the black hole itself!” lead author Lars Fuhrmann explained. “This has serious implications for the physical processes producing the gamma-ray photons.”

The researchers are currently collecting more data for use in thorough follow-up reports to this announcement.

Read more: http://www.iflscience.com/space/researchers-identify-origin-violent-gamma-ray-outbursts

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