#frbs

Fast radio bursts (FRBs) are sudden and intense blasts of radio wave energy from deep space that remain one of the most intriguing mysteries in astrophysics, and a new study adds valuable insight into what might be generating them. Led by a team from the Italian National Institute for Astrophysics (INAF), researchers looked at FRB 20201124A, first discovered in 2020. Specifically, they analyzed a persistent radio source (PRS) near the FRB.

One Cosmic Mystery Illuminates Another, As Fast Radio Burst Intercepts A Galactic Halo

“Although scientists have studied [Fast Radio Bursts] intensely since their discovery, their origins remain mysterious. Meanwhile, an estimated 2 trillion galaxies populate our observable Universe. With incredibly large distances for FRBs to traverse, each one risks passing through an intervening galaxy. Giving off multiple pulses of under 40 microseconds apiece, FRB 181112 became the first burst to intercept a galactic halo.”

Where do fast radio bursts come from? Recent studies have demonstrated that they’re associated with host galaxies, but we don’t understand how they work, why some of them repeat, or why the pulse durations are so variable.

What about galactic halos: how much gas is in them? What is the gas temperature, density, magnetization, etc.? These are big questions about galaxies in general that we don’t have a general picture of. If only there were some way to learn more.

The CHIME radio telescope in British Columbia (pictured) found that a repeating source of radio waves from deep space has a brief window of activity about every 16 days.

CREDIT: CHIME COLLABORATION

A periodic flurry of radio waves from some unknown object in deep space could help astronomers figure out what’s triggering similar radio bursts in other galaxies.

Since 2007, researchers have cataloged over 100 fast radio bursts, or FRBs, coming from every direction in the sky. But it’s unknown what causes these radio bursts. Only 10 have been seen to repeat (SN: 8/14/19), and none of those had exhibited any sort of steady tempo — until now.

One of the known repeaters has a relatively brief window of activity about every 16 days, researchers report January 28 at arXiv.org. That means something about the source or its environment is reliably controlling the burst activity, a potential clue to the true nature of these enigmatic objects.

Dongzi Li, an astrophysicist at the University of Toronto, and colleagues found the pattern in data from the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, radio telescope in British Columbia. They determined that the FRB blasts out about one to two radio bursts per hour for four days and then goes silent for just over 12 days before usually repeating the cycle.

“This is very significant,” says Duncan Lorimer, an astrophysicist at West Virginia University in Morgantown and co-discoverer of the first FRB (SN: 7/25/14). “It’s potentially going to take us in an interesting direction to get to the bottom of these repeaters.”

One possible explanation for the periodicity is that the FRB is orbiting something else, perhaps a star or black hole. In that case, the 16-day period might reveal how often the source of the radio waves is pointed toward Earth.

Alternatively, stellar winds from a companion might periodically boost or block the radio pulses. Winds might also explain why not every 16-day cycle produces bursts: If the companion occasionally belches out more material than usual, that could mask the FRB’s signal.

Either explanation implies that repeating FRBs — or at least, this one — might come paired with something else.

Li and her colleagues aren’t ready to rule out stand-alone objects, where the 16-day period might arise from the FRB rotating or wobbling. But that scenario is a bit tougher to reconcile with the data. For example, one popular FRB culprit is a type of highly magnetic neutron star known as a magnetar. But known magnetars in our galaxy spin around once every 12 seconds or less, the team notes, a far cry from the fortnight needed for this FRB.

This particular radio burst was also recently traced to a star-forming region in a spiral galaxy nearly 500 million light-years away from Earth (SN: 1/6/20). Future scans of its home with telescopes sensitive to other electromagnetic radiation, such as X-rays or gamma rays, might whittle down the list of suspects and move astronomers closer to solving this cosmic mystery.

Sep. 24, 2018, 1:09 PM EDTBy Jeremy Hsu

For the past decade, scientists have been puzzling over powerful, millisecond-long flashes of energy from deep space. Some scientists think these “fast radio bursts,” or FRBs, come from natural sources, such as newborn neutron stars or black holes. Others think they could be signals from alien civilizations.

One thing’s for sure: FRBs are more common than we realized. In the latest discovery, scientists working as part of a $100-million initiative known as Breakthrough Listen used artificial intelligence to detect dozens of additional FRBs coming from FRB 121102, an as-yet-uncharacterized source in a galaxy 3 billion light-years from Earth.

The work is the first step in the initiative’s grander plans for using AI to find hidden patterns in the bigger sea of cosmic signals that come our way — research that could finally provide an answer to that eternal question: Are we alone in the universe?

"It's a great way of developing the kinds of techniques that we ultimately want to use to find other types of signals that might come from extraterrestrial intelligence," says Andrew Siemion, principal investigator for Breakthrough Listen and director of the Search for Extraterrestrial Intelligence (SETI) Research Center at the University of California, Berkeley.

In August 2017, the Breakthrough Listen team discovered 21 fast radio bursts from FRB 121102 during five hours of observations made by a radio telescope in Green Bank, West Virginia. In their latest study, which will be published in an upcoming issue of the Astrophysical Journal, the researchers deployed a specialized AI technique known as deep learning to see if any signals had been overlooked in their initial research.

Siemion gave Yunfan "Gerry" Zhang, a doctoral student at Berkeley, the job of training a deep learning algorithm to hunt for the additional bursts. The trained AI was turned loose to sort through 400 terabytes of observational data — a huge trove containing about as much data as is contained in 40,000 hours of 4K video.

After a month of work, Zhang strolled into Siemion's office and told his stunned mentor that he had discovered about 100 previously undetected bursts. To be sure Zhang was right, the researchers used standard computer software to clean up the messy signals — and confirmed the existence of at least 72 additional bursts.

The same AI approach could help astronomers find new repeating sources of fast radio bursts closer to Earth than FRB 121102. If closer repeater sources do exist, astronomers might be able to get a better look at them using optical and X-ray telescopes, says Harvard astrophysicist Avi Loeb, the science theory director for all initiatives funded by the Breakthrough Prize Foundation.

"We still have no new clue on whether the origin is artificial or natural," said Loeb, who was not directly involved in the Breakthrough Listen work.

Loeb had previously examined the possibility that fast radio bursts come from radio transmitters constructed by an advanced alien civilization — perhaps evidence of powerful energy beams used to propel alien starships. He also theorized that repeater sources such as FRB 121102 are more likely to be such alien signals because natural origin explanations would most likely produce only a single burst.

But the Breakthrough Listen team is already looking beyond fast radio bursts. It's developing AI to analyze a wider range of similarly interesting signals coming from nearby stars and galaxies. In this case, AI's broad pattern recognition abilities could prove especially helpful when nobody knows exactly what an alien signal might look like.

"If AI could flag things that don’t look right or don’t look natural, that might be an interesting thing to do," says Seth Shostak, a senior astronomer at the SETI Institute in California who was not involved in the Breakthrough Listen study.

Fast radio bursts (FRBs), fleeting blasts of energy from space, are a cosmic enigma. “Fast radio bursts are one of astronomy’s greatest mysteries,” says lead author Mohit Bhardwaj, a member of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) collaboration and a postdoctoral fellow at Carnegie Mellon University. “These extremely powerful radio blasts can travel cosmological distances and emit more energy than the sun does in a thousand years, despite lasting only a few thousandths of a second. Even more intriguing is that, though they hit the Earth roughly every minute from all over the sky, their origin is still unknown.”