From The University of Birmingham (UK) Via “” : “Gamma-ray burst is ‘Rosetta Stone’ for finding neutron star collisions”

From The University of Birmingham (UK)




Artist’s impression of GRB 211211A. Credit: Soheb Mandhai @TheAstroPhoenix

A highly unusual blast of high-energy light from a nearby galaxy has been linked by scientists to a neutron star merger.

The event, detected in December 2021 by NASA’s Neil Gehrels Swift Observatory and the Fermi Gamma-ray Space Telescope, was a gamma-ray burst—an immensely energetic explosion which can last from a few milliseconds to several hours.

This gamma-ray burst, identified as GRB 211211A, lasted about a minute—a relatively lengthy explosion, which would usually signal the collapse of a massive star into a supernova. But this event contained an excess of infrared light and was much fainter and faster-fading than a classical supernova, hinting that something different was going on.

In a new study, published in Nature [below], an international team of scientists showed that the infrared light detected in the burst came from a kilonova. This is a rare event, thought to be generated as neutron stars, or a neutron star and a black hole collide, producing heavy elements such as gold and platinum. Thus far, these events, called kilonovae, have only been associated with gamma-ray bursts with durations of less than two seconds.

The work was led by Jillian Rastinejad at Northwestern University along with physicists from the University of Birmingham (UK) and the University of Leicester (UK), and Radboud University (NL).

Dr. Matt Nicholl, an Associate Professor at the University of Birmingham, modeled the kilonova emission. “We found that this one event produced about 1,000 times the mass of the Earth in very heavy elements. This supports the idea that these kilonovae are the main factories of gold in the universe,” he said.

Although up to 10% of long gamma-ray bursts are suspected to be caused by the merging of neutron star or neutron stars and black holes, no firm evidence—in the form of kilonovae—had previously been identified.

Dr. Gavin Lamb, a post-doctoral researcher at the University of Leicester, explained: “A gamma-ray burst is followed by an afterglow that can last several days. These afterglows behave in a very characteristic manner, and by modeling them we can expose any extra emission components, such as a supernova or a kilonova.”

The kilonova generated by GRB 211211A is the closest to have been discovered without gravitational waves, and has exciting implications for the upcoming gravitational wave observation run, starting in 2023. Its proximity in a neighboring galaxy only 1bn light years away gave scientists the opportunity to study the properties of the merger in unprecedented detail.

A related paper from the same collaboration in Nature Astronomy [below], led by Dr. Benjamin Gompertz, Assistant Professor at the University of Birmingham, describes some of these properties.

In particular, the team identified how the jet of high energy electrons, traveling at almost the speed of light and causing the gamma-ray burst, changed with time. The cooling down of this jet was shown to be responsible for the long lasting GRB emission.

In the paper, the team also described how close observation of GRB 211211A can offer fascinating insights into other previously unexplained gamma-ray bursts which have appeared not to fit with standard interpretations.

Dr. Gompertz said, “This was a remarkable GRB. We don’t expect mergers to last more than about two seconds. Somehow, this one powered a jet for almost a full minute. It’s possible the behavior could be explained by a long-lasting neutron star, but we can’t rule out that what we saw was a neutron star being ripped apart by a black hole.

“Studying more of these events will help us determine which is the right answer and the detailed information we gained from GRB 211211A will be invaluable for this interpretation.”

Science papers:
Nature Astronomy

See the full article here .

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The University of Birmingham (UK) has been challenging and developing great minds for more than a century. Characterized by a tradition of innovation, research at the University has broken new ground, pushed forward the boundaries of knowledge and made an impact on people’s lives. We continue this tradition today and have ambitions for a future that will embed our work and recognition of the Birmingham name on the international stage.

The University of Birmingham is a public research university located in Edgbaston, Birmingham, United Kingdom. It received its royal charter in 1900 as a successor to Queen’s College, Birmingham (founded in 1825 as the Birmingham School of Medicine and Surgery), and Mason Science College (established in 1875 by Sir Josiah Mason), making it the first English civic or ‘red brick’ university to receive its own royal charter. It is a founding member of both the Russell Group (UK) of British research universities and the international network of research universities, Universitas 21.

The student population includes 23,155 undergraduate and 12,605 postgraduate students, which is the 7th largest in the UK (out of 169). The annual income of the institution for 2019–20 was £737.3 million of which £140.4 million was from research grants and contracts, with an expenditure of £667.4 million.

The university is home to the Barber Institute of Fine Arts, housing works by Van Gogh, Picasso and Monet; the Shakespeare Institute; the Cadbury Research Library, home to the Mingana Collection of Middle Eastern manuscripts; the Lapworth Museum of Geology; and the 100-metre Joseph Chamberlain Memorial Clock Tower, which is a prominent landmark visible from many parts of the city. Academics and alumni of the university include former British Prime Ministers Neville Chamberlain and Stanley Baldwin, the British composer Sir Edward Elgar and eleven Nobel laureates.

Scientific discoveries and inventions

The university has been involved in many scientific breakthroughs and inventions. From 1925 until 1948, Sir Norman Haworth was Professor and Director of the Department of Chemistry. He was appointed Dean of the Faculty of Science and acted as Vice-Principal from 1947 until 1948. His research focused predominantly on carbohydrate chemistry in which he confirmed a number of structures of optically active sugars. By 1928, he had deduced and confirmed the structures of maltose, cellobiose, lactose, gentiobiose, melibiose, gentianose, raffinose, as well as the glucoside ring tautomeric structure of aldose sugars. His research helped to define the basic features of the starch, cellulose, glycogen, inulin and xylan molecules. He also contributed towards solving the problems with bacterial polysaccharides. He was a recipient of the Nobel Prize in Chemistry in 1937.

The cavity magnetron was developed in the Department of Physics by Sir John Randall, Harry Boot and James Sayers. This was vital to the Allied victory in World War II. In 1940, the Frisch–Peierls memorandum, a document which demonstrated that the atomic bomb was more than simply theoretically possible, was written in the Physics Department by Sir Rudolf Peierls and Otto Frisch. The university also hosted early work on gaseous diffusion in the Chemistry department when it was located in the Hills building.

Physicist Sir Mark Oliphant made a proposal for the construction of a proton-synchrotron in 1943, however he made no assertion that the machine would work. In 1945, phase stability was discovered; consequently, the proposal was revived, and construction of a machine that could surpass proton energies of 1 GeV began at the university. However, because of lack of funds, the machine did not start until 1953. The DOE’s Brookhaven National Laboratory (US) managed to beat them; they started their Cosmotron in 1952, and had it entirely working in 1953, before the University of Birmingham.

In 1947, Sir Peter Medawar was appointed Mason Professor of Zoology at the university. His work involved investigating the phenomenon of tolerance and transplantation immunity. He collaborated with Rupert E. Billingham and they did research on problems of pigmentation and skin grafting in cattle. They used skin grafting to differentiate between monozygotic and dizygotic twins in cattle. Taking the earlier research of R. D. Owen into consideration, they concluded that actively acquired tolerance of homografts could be artificially reproduced. For this research, Medawar was elected a Fellow of the Royal Society. He left Birmingham in 1951 and joined the faculty at University College London (UK), where he continued his research on transplantation immunity. He was a recipient of the Nobel Prize in Physiology or Medicine in 1960.