A global team of astronomers has discovered a long gamma-ray burst in an ancient galaxy, most likely brought on by two separate neutron stars merging, tough traditional understanding about the reasons for such bursts. The team used multiple telescopes to examine the 2019 burst, and though other potential causes are considered, they hope future observations will clarify the phenomenons origins.
For the very first time, a worldwide group of astronomers has observed a long gamma-ray burst near the center of an ancient galaxy. This is unique because these sort of gamma-ray bursts generally take place when huge stars collapse or when neutron stars circle each other for a very long time, and there are no such stars at the center of ancient galaxies. The team, led by Andrew Levan (Radboud University), published their findings in Nature Astronomy.
The general agreement utilized to be that long gamma-ray bursts of a minimum of a few seconds can only happen when a very heavy star collapses into a supernova at the end of its life. In 2022, a second potential trigger of long gamma-ray bursts was discovered when 2 big stars, which had been orbiting each other all their lives, turned into neutron stars at the end and collided into a kilonova. Now in 2023, it seems that long gamma-ray bursts can take place in a third method.
” Our information indicate that this is a case of 2 different neutron stars merging. So not neutron stars that have been together all their lives,” says lead scientist Andrew Levan (Radboud University). “We suspect that the neutron stars were pushed together by the gravity of the lots of surrounding stars at the center of the galaxy.”
The team of scientists studied the after-effects of a gamma-ray burst observed by the Neil Gehrels Swift Observatory on October 19, 2019. They did so utilizing the Gemini South telescope in Chile, the Nordic Optical Telescope on the Canary Island of La Palma, and the Hubble Space Telescope.
Their observations show that the burst was caused near the center of an ancient galaxy. This immediately provides 2 arguments pointing to the combining of two sources.
The very first argument is that there are almost no heavy stars in ancient galaxies that could collapse into supernovae, due to the fact that heavy stars usually take place in young galaxies. In addition, supernovae emit bright optical light, which was not observed in this case.
A second argument is that the center of galaxies are busy locations. There are numerous thousands of regular stars, white overshadows, neutron stars, great voids, and dust clouds all orbiting a supermassive black hole. Completely, this represents over 10 million items and stars crammed into a space of a few light-years throughout. “That is an area similar to the distance between our sun and the next star,” Levan describes. “So the possibility of an accident in the center of a galaxy is much higher than, say, at the outskirts, where we are.”
The researchers are still leaving space for alternative descriptions. The prolonged gamma-ray burst might also arise from the collision of compact things aside from neutron stars, for instance, great voids or white overshadows. In the future, the researchers intend to have the ability to observe long gamma-ray bursts at the very same time as gravitational waves. This would assist them to make more definitive statements about the origin of the radiation.
For more on this discovery:
Referral: “A long-duration gamma-ray burst of dynamical origin from the nucleus of an ancient galaxy” by Andrew J. Levan, Daniele B. Malesani, Benjamin P. Gompertz, Anya E. Nugent, Matt Nicholl, Samantha R. Oates, Daniel A. Perley, Jillian Rastinejad, Brian D. Metzger, Steve Schulze, Elizabeth R. Stanway, Anne Inkenhaag, Tayyaba Zafar, J. Feliciano Agüí Fernández, Ashley A. Chrimes, Kornpob Bhirombhakdi, Antonio de Ugarte Postigo, Wen-fai Fong, Andrew S. Fruchter, Giacomo Fragione, Johan P. U. Fynbo, Nicola Gaspari, Kasper E. Heintz, Jens Hjorth, Pall Jakobsson, Peter G. Jonker, Gavin P. Lamb, Ilya Mandel, Soheb Mandhai, Maria E. Ravasio, Jesper Sollerman and Nial R. Tanvir, 22 June 2023, Nature Astronomy.DOI: 10.1038/ s41550-023-01998-8.
There are hundreds of thousands of normal stars, white dwarfs, neutron stars, black holes, and dust clouds all orbiting a supermassive black hole. The prolonged gamma-ray burst might likewise result from the accident of compact objects other than neutron stars, for example, black holes or white overshadows.
This is special since these kinds of gamma-ray bursts usually happen when massive stars collapse or when neutron stars circle each other for a long time, and there are no such stars at the center of ancient galaxies. In 2022, a second potential trigger of long gamma-ray bursts was discovered when 2 big stars, which had been orbiting each other all their lives, turned into neutron stars at the end and collided into a kilonova. “We suspect that the neutron stars were pushed together by the gravity of the lots of surrounding stars at the center of the galaxy.”