(ORDO NEWS) — Like gravitational waves (GWs) and gamma-ray bursts (GRBs), fast radio bursts (FRBs) are one of the most powerful and mysterious astronomical phenomena to date.
These short-term events consist of bursts that emit more energy in a millisecond than the Sun does in three days.
Although most bursts last only milliseconds, there have been rare instances where FRBs have been found to be repetitive.
While astronomers are still not sure what causes them, and opinions differ, dedicated observatories and international collaboration have greatly increased the number of events available for study.
The next generation radio telescope located at the Dominion Radio Astrophysical Observatory (DRAO) in British Columbia, Canada.
With its large field of view and wide frequency coverage, this telescope is an indispensable tool for detecting FRBs (more than 1000 sources to date!).
Using a new type of algorithm, the CHIME/FRB collaboration found evidence of 25 new recurring FRBs in the CHIME data that were discovered between 2019 and 2021.
Despite their mysterious nature, FRBs are ubiquitous, and the best estimate is that events occur on Earth about a thousand times a day across the sky.
None of the theories or models proposed to date can fully explain all the properties of bursts or their sources.
While some are thought to be caused by neutron stars and black holes (attributed to the high energy density of their environment), others continue to defy the classification.
Because of this, other theories persist, from pulsars and magnetars to gamma-ray bursts and extraterrestrial communication.
CHIME was originally designed to measure the expansion history of the universe through the detection of neutral hydrogen.
About 370,000 years after the Big Bang, the universe was permeated with this gas, and the only photons were either the cosmic microwave background (CMB) from the Big Bang or emitted by neutral hydrogen atoms.
For this reason, astronomers and cosmologists refer to this period as the “Dark Ages,” which ended about 1 billion years after the Big Bang, when the first stars and galaxies began reionizing neutral hydrogen (the era of reionization).
In particular, CHIME was designed to determine the wavelength of light that neutral hydrogen absorbs and emits, known as the 21 cm hydrogen line.
In this way, astronomers could measure how fast the universe expanded during the “Dark Ages” and make comparisons with later observable cosmological epochs.
However, CHIME has since proven to be ideal for learning FRB. , thanks to the wide field of view and the covered frequency range (from 400 to 800 MHz).
This is the goal of the CHIME/FRB Collaboration, which is to discover and characterize FRBs and trace them back to their sources.
As Dunlap Fellow and lead author Ziggy Pleunis told Universe Today, each FRB is described by its position in the sky and a quantity known as its dispersion measure (DM).
This refers to the time delay between high and low frequencies caused by the interaction of the flash with the material as it moves through space.
In an article published in August 2021, the CHIME/FRB collaboration presented the first large sample of the FRB catalog containing 536 events detected by CHIME between 2018 and 2019, including 62 bursts from 18 previously recorded repeating sources.
For this latest study, Pleunis and colleagues used a new clustering algorithm that looks for multiple events that are aligned in the sky with similar DMs.
“We can measure the position of the fast radio burst in the sky and measure the dispersion to a certain accuracy, which depends on the design of the telescope being used,” Pleunis said.
“The clustering algorithm takes into account all fast radio bursts detected by the CHIME telescope and looks for FRB clusters that have consistent sky positions and dispersion measures within measurement errors.
We then run various checks to make sure the spikes in the cluster are indeed coming from the same source.”
Of the over 1000 FRBs found to date, only 29 have been identified as being repetitive in nature. Moreover, it has been found that virtually all recurring FRBs recur irregularly.
The only exception is FRB 180916 discovered by CHIME researchers in 2018 (reported in 2020). repetitive sources, almost doubling the number available for study.
In addition, the team noted some very interesting features that may provide insight into their causes and characteristics. As Pleunis added:
“If we carefully count all of our fast radio bursts and sources that repeat, we find that only about 2.6% of all the fast radio bursts we detect are repeats.
For many new sources, we found only a few bursts, making the sources completely inactive. Almost as inactive as the sources we only saw once.
“Therefore, we cannot exclude that sources for which we have observed only one burst so far will eventually also show repeated bursts.
It is possible that all sources of fast radio bursts eventually repeat, but many sources are not very active.
Any explanation for fast radio bursts must explain why some sources are hyperactive while others are mostly quiet. ”
These results may help in future research that will benefit from the next generation of radio telescopes that will come online in the coming years.
These include “Square Kilometer”. The Massive Observatory (SKAO), which is expected to collect its first light by 2027.
At the same time, the tremendous rate at which new FRBs are being detected (including recurring events) could mean that radio astronomers could be close to a breakthrough!
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