Indian astronomers part of team that detected 'fizzled shortest gamma-ray burst'

A group of astronomers, including from India, have detected a very short, powerful burst of high-energy radiation that lasted for about a second and had been racing towards Earth for nearly half the present age of the universe. According to a statement by the Ministry of Science and Technology, the burst detected by NASA’s Fermi Gamma-ray Space Telescope turned out to be one for the record books—the shortest gamma-ray burst (GRB) caused by the death of a massive star. NASA’s Fermi Gamma-ray Space Telescope detected a pulse of high-energy radiation that lasted for only about a second. 

According to a NASA press release, GRBs are the most powerful events in the universe, detectable across billions of light-years. Astronomers classify them as long or short based on whether the event lasts for more or less than two seconds. The US space agency said that scientists observe long bursts in association with the demise of massive stars, while short bursts have been linked to a different scenario.

Discovery helps resolve issues related to GRB

The identification of this short event, which involved several scientists across the world, including Shashi Bhushan Pandey from Aryabhatta Research Institute of Observational Sciences (ARIES), an institute of the Department of Science and Technology (DST), as well as scientists from other Indian institutions, showed for the first time that a dying star can produce short bursts too. According to PTI, from India, the Inter-University Centre for Astronomy and Astrophysics, Pune (IUCAA), National Centre for Radio Astrophysics - Tata Institute of Fundamental Research, Pune (NCRA), and IIT Mumbai also participated in this work.

Bin-bin Zhang at Nanjing University in China and the University of Nevada, Las Vegas, said, “We already knew some GRBs from massive stars could register as short GRBs, but we thought this was due to instrumental limitations. Now we know dying stars can produce short bursts, too”. 

In a separate statement, Shashi Bhushan Pandey explained, “Such a discovery has helped to resolve the long-standing issues related to gamma-ray bursts. Also, this study triggers to re-analyse all such known events to constrain number densities better”. 

GRB 200826A lasted for 0.65 seconds 

Named GRB 200826A, after the date it occurred, the burst is the subject of two papers published in Nature Astronomy on July 26. The first, led by Zhang, explores the gamma-ray data. The second, led by Tomás Ahumada, a doctoral student at the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, describes the GRB’s fading multiwavelength afterglow and the emerging light of the supernova explosion that followed.

“We think this event was effectively a fizzle, one that was close to not happening at all,” Ahumada said. “Even so, the burst emitted 14 million times the energy released by the entire Milky Way galaxy over the same amount of time, making it one of the most energetic short-duration GRBs ever seen,” he added. 

NASA explained that when a star much more massive than the Sun runs out of fuel, its core suddenly collapses and forms a black hole. As matter swirls toward the black hole, some of it escapes in the form of two powerful jets that rush outward at almost the speed of light in opposite directions, the US space agency said. It added that astronomers only detect a GRB when one of these jets happens to point almost directly toward Earth.

NASA also said that GRB 200826A was a sharp blast of high-energy emission lasting just 0.65 seconds. After travelling for eons through the expanding universe, the signal had stretched out to about one second long when it was detected by Fermi’s Gamma-ray Burst Monitor. It is worth noting that the event also appeared in instruments aboard NASA’s Wind mission, which orbits a point between Earth and the Sun located about 930,000 miles (1.5 million kilometres) away, and Mars Odyssey, which has been orbiting the Red Planet since 2001. 

(With inputs from PTI)