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For the first time, astrophysicists have assembled observational evidence of a fast radio blast that likely traveled to Earth from a particular type of neutron star in our galaxy, the Milky Way, according to three new studies.
In addition, X-ray emissions accompanied the outbreak, which is also the first.
Fast radio bursts, or FRBs, are bright and powerful emissions of radio waves ranging from a fraction of a millisecond to a few milliseconds.
Until now, it has been reported that these kinds of explosions occur in distant galaxies, traveling across the universe to reach our planet.
But they remain mysterious, and astronomers have yet to determine what caused the explosions.
Neutron stars, or dense remnants of giant stars from a supernova explosion, have been a common candidate for the potential source of FRB.
More specifically, the scientists focused on neutron stars with extremely powerful magnetic fields, called magnetars, as the main contenders.
In line with this hypothesis, the probable point of origin of the fast radio burst inside our galaxy is a magnetar called SGR 1935 + 2154, according to the scientists.
Since the discovery of fast radio bursts in 2007, scientists have devoted efforts to identifying the sources of extragalactic phenomena – those that may exist outside the Milky Way.
However, the research and theories proposed for their origin have exceeded the number of FRBs that have occurred in recent years.
The short lifespan of FRBs also makes them difficult to identify and study.
Crucial clue
This is why the FRB of a magnetar coming from the Milky Way, rather than outside it, is a crucial clue in this research.
An international team of scientists led the charge to unlock this space mystery by conducting a series of observations and experiments, with the help of satellite and ground-based telescopes.
“FBR 200428 is the first FRB for which emissions other than radio waves have been detected, the first to be found in the Milky Way and the first to be associated with a magnetar,” said Amanda Weltman and Anthony Walters, both involved in a review of the study.
Weltman is a theoretical physicist working in the Cosmology and Gravity group, while Walters is a scholar in the high energy theory, cosmology, and astrophysics group.
“It is also the brightest radio flash of a galactic magnetar that has been measured so far, which potentially solves a key conundrum in this area,” they added.
In fact, the discovery was truly collaborative on a global scale – the Neil Gehrels Swift Observatory and Fermi Gamma-ray Space Telescope reported multiple bursts of X-ray emission from the magnetar on April 27, 2020.
The next day, the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, FRB project reported an explosion with two sub-bursts from the approximate direction of the magnetar during “unusually intense X-ray burst activity,” the study says.
“To see the explosions from such a great distance, they must be tens of thousands to millions of times more powerful than anything we have detected in our galaxy,” Daniele Michilli, a postdoctoral researcher, said in a study briefing.
Researchers from the Survey for Transient Astronomical Radio Emission 2, or STARE2, based in the southwestern United States, confirmed that an event was detected at roughly the same time and in the same region as the CHIME event.
Several other telescopes and detectors, including Russia’s Konus detector aboard NASA’s Wind spacecraft, the European Space Agency’s INTEGRAL telescope, and the Chinese space observatory Insight, have reported bursts of X-rays from the magnetar simultaneously with the FRB.
“This result is also a great example of how when international teams of scientists come together to study a phenomenon in different ways, we learn more,” said study author Christopher Bochenek.
“What’s really amazing is that we’ve seen something from our galaxy, given how rare these extragalactic FRBs are that we didn’t have to wait 50 years to detect a fast radio blast in the Milky Way,” he added.
“We only had to wait a few.”
Possible production
Because no bright radio bursts from galactic magnetars had previously been observed, Weltman and Walters said, the magnetars inside the Milky Way seemed an unlikely source.
Questions remain as to what could cause bright and rare radio flashes with X-ray counterparts, but there are several possibilities.
Magnetars may be the progenitors because their strong magnetic fields could act as “motors” that drive FRBs, they added.
A flare from a magnetar may have collided and generated a shock wave.
Given “the large energy and activity gaps between the brightest and most active FRB sources and what is observed for magnetars, perhaps younger, more energetic and active magnetars are needed to explain all the FRB observations,” said Paul Scholz. , who is a co-author of the study from the CHIME group.
Although the China-based FAST, or five-hundred-meter-aperture spherical telescope did not observe the specific FRB, the team observed enough to conclude that fast radio bursts associated with short bursts of X-rays are rare.
“This paper has provided a complete picture of the association, but the origin is unknown,” said FAST study author Bing Zhang, distinguished professor and associate dean for research in the University of Nevada science department.
The discovery provides another clue to the cosmic mystery of fast radio bursts and “underscores the need for international scientific cooperation in astronomy and coverage of the sky from multiple locations,” Weltman and Walters said.
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