Friday, August 5, 2022

Mysterious burst of energy observed for the first time in radio astronomy

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One of the most powerful flashes in the sky, the result of a star and neutron star colliding, has been observed for the first time by millimeter-wave radio astronomy, providing an unprecedented look at one of the most violent events in the cosmos.

A research team led by Northwestern University in Illinois and Radboud University in the Netherlands used the Atacama Large Millimeter/submillimeter Array or ALMA radio telescope in Chile to capture the afterglow of GRB 211106A, a short gamma-ray burst (GRB) originating from a galaxy 20 billion light years away.

“This brief gamma-ray burst marked the first time we attempted to observe such an event with ALMA,” Northwestern professor of physics and astronomy Wen-fai Fong said in a statement. “Afterglows for short bursts are very hard to come by, so to see this event shine so brightly was spectacular.

dr Fong is one of many authors of a study on the observation that will be published in an upcoming issue of Astrophysical Journal Lettersand is now available online at the academic preprint archive arxiv.org.

GRBs are powerful bursts of gamma rays that occur when massive stars collapse into black holes or dense neutron stars in a binary system merge with their companion stars to form a black hole, an intense cataclysmic event thought to be the most massive Black hole elements form universe like gold and plutonium.

“These mergers occur because of gravitational-wave radiation, which siphons energy from the binary stars’ orbit and causes the stars to spiral toward each other,” Radboud University astronomer and lead author of the publication Tanmoy Laskar said in a statement. “The resulting explosion is accompanied by jets traveling at nearly the speed of light. When one of these jets is aimed at Earth, we observe a short pulse of gamma rays, or a short-lived GRB.”

Short GRBs can last only a fraction of a second, but their afterglow can last for minutes or even days at longer, lower-energy wavelengths of light.

Such was the case of GRB 211106A, whose afterglow was first detected in X-ray light from NASA’s Neil Gehrel’s Swift Observatory, then in infrared light from the Hubble Space Telescope, and finally in millimeter radio light from ALMA. Only with the addition of the ALMA observation could the GRB be located in a distant galaxy.

“The Hubble observations revealed a steady field of galaxies,” said Dr. Laskar in a statement. “ALMA’s unprecedented sensitivity allowed us to more accurately pinpoint the position of the GRB in this field, and it turned out to be in another faint galaxy, more distant. This in turn means this brief gamma-ray burst is even stronger than we first thought, making it one of the brightest and most energetic on record.”

according to dr Fong, the millimeter wavelength also gave scientists a clearer picture of the structure and density of the area around the GRB, and even allowed researchers to measure the apparent width of the beam, which triggered the burst at just over 15 degrees. one of the widest ever measured.

The study underscores the value of observing complex phenomena at multiple wavelengths using the most advanced instruments available, which now include the newly commissioned James Webb Space Telescope.

“In the future, we could also use JWST to detect infrared afterglows and study their chemical composition,” said Dr. Laskar in a statement. “I am excited about these upcoming discoveries in our field.”

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