الثلاثاء، 9 يونيو 2020

Astronomers Identify 157-Day Cycle in Ultra-Powerful Radio Bursts from Space

The only repeating FRB ever discovered, located in a dwarf galaxy 3 billion light years away.

There are a lot of things in the universe that we don’t fully understand, and Fast Radio Bursts (FRBs) are at the top of the list. We didn’t even know these phenomena even existed until 2007, and since then we’ve seen dozens of these seemingly random bursts of energy. Recently, teams from around the world have started to spot recurring FRBs, and they may have a pattern. A new analysis of one particular FRB source says it exhibits a 157-day activity cycle, which might help us figure out what’s causing it in the first place. 

The first recorded FRB occurred in 2001, but the data wasn’t analyzed until 2007. Scientists have been perplexed by FRBs ever since. These events only last fractions of a second, but they release enough radio frequency energy to outshine millions of stars. Only a handful of FRBs have been shown to repeat, including FRB 121102. That was the first FRB known to repeat, and now it’s only the second to display a predictable cycle of flashes. 

Research out of the University of Manchester shows a 157-day cycle of activity from FRB 121102. Over a year-long observation campaign with the Lovell Telescope, the team detected 32 bursts from this object. From that, the team was able to describe a pattern consisting of frequent bursts for a period of 90 days followed by a pause of about 67 days. Then the whole cycle starts over. 

Over the years, astronomers have suggested just about everything as a possible explanation for FRBs including energetic supernovae, dark matter collapsing pulsars, and black holes colliding with neutron stars. With multiple repeating FRBs known to exist, many of these hypotheses have lost favor. 

The Lovell Telescope.

The discovery of repeating patterns helps narrow the focus of researchers even more. The team speculates that the repeating pattern may be connected to orbital motion. For example, a high-mass binary system involving neutron stars or magnetars could emit FRBs by some process we don’t currently understand as they orbit each other. No one can say why some FRBs appear to repeat, and others don’t. There could be multiple types of FRBs, and only some repeat. Or maybe all of them repeat, but most patterns are so slow that we don’t have enough data to confirm that. 

More research will be necessary to confirm the pattern of FRB 121102. If the researchers are right, a new period of activity should have started on June 2nd.

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