Eccentric forces of gamma ray burst revision of the theoretical framework

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Deep Space Discovery: Oddball's Gamma-Ray Burst A Revision of the Theoretical Framework

Submission of the artist. Credit: Anyu Lei and Jing Chen, Nanjing University College of Art

The mysteries of the universe continue to fascinate astronomers, and with each new observation comes an opportunity to deepen–or overturn–our understanding of the cosmos.


In the December 7 issue of the magazine natureAn international team of astrophysicists reports the discovery of a unique cosmic gamma-ray burst (GRB) that challenges prevailing theories about how violent cosmic explosions form. This outburst of “eccentricity” led the team to propose a new model or source for certain types of GRBs.

Gamma ray bursts are the brightest and most violent explosions in the universe. They indicate the death of stars or the collision of star remnants. Observed GRBs are usually placed into two categories: short-term or long-term GRBs. Long GRBs arise from the death of massive stars, and are usually associated with bright optical transits called supernovae. Short GRBs last less than 2 seconds and originate from collisions of 2 seconds duration Neutron stars or a neutron star and a black hole, and are usually associated with more faint optical transients known as kilonovas.

For decades, GRBs have nestled nicely in these cozy categories. Until now.

On December 11, 2021, the GRB launched several gamma-ray detectors into space, including NASA’s Fermi Gamma-Ray Telescope and the Neil Gehrels Swift Observatory. This burst, approximately 70 seconds long, is usually seen as a normal long GRB. That is, until multiple teams from the US and Europe made follow-up observations and surprisingly discovered a signature.

“This GRB model has two parts: a sharp 13-second rise and a softer, extended emission of 55 seconds,” said Bin-Ben Zhang, a NYLV alumnus and corresponding author of the study, who is now at China’s Nanjing University. “The duration of the 13-second sharp spike should have completely ruled out this short GRB rush.”

In other words, rather than showing a much brighter supernova, as expected, the observation was consistent with the kilonova typically associated with short supernovae.

“Such a strange GRB was the first of its kind ever,” said Peng Zhang, a professor of astrophysics at UNLV. nature paper. “This discovery not only challenged our understanding of the origins of GRBs, but also required us to consider a new model of how some GRBs form.”

The research team believes that the unique GRB, known as GRB 211211A, likely formed through the collision between a neutron star and a white dwarf, which is known as a WD-NS merger.

White dwarfs are Earth-sized objects that form from the death of low-mass stars — those less than one-eighth as massive as our sun. Neutron stars form when they get bigger huge stars, those with masses between about eight and 20 suns, die. When larger stars die, they form black holes directly.

Massive, low-density stars make long-period GRBs while high-density stars, including neutron stars, make short-period GRBs. According to Zhang from UNLV, white dwarfs It has a medium density, which makes it an ideal asset for a type of GRB discovered in 2021 because it displays a long duration on the spot without involving a massive star.

“Despite the relatively large number of GRBs observed each year, the unique signature of GRB 211211A pushed the envelope of our existing categorical systems and required a new way of thinking,” said Zhang. “After careful review, the only logical merger scenario was that of a white dwarf and a neutron star.”

UNLV doctoral student Shunke Ai and a student from Nanjing University collaborated to develop a detailed model to interpret the strange kilonova signature observed by GRB 211211A. Ai found that if the WD-NS merger left behind a fast-spinning neutron star, known as a magnetar, the injection of extra energy from the magnetar along with nuclear reaction energy from the material ejected during the explosion could explain the kilonova emission observed in GRB 211211A. .

the study, “A long-period gamma-ray burst with a strange originappeared on the December 7 issue of the magazine nature. The paper includes 10 co-authors from 4 institutions, with UNLV and Nanjing University being the lead institutions. Published in the same issue three Collimated Leaves which reports the discovery of a kilonova. This paper focuses on the strange gamma-ray emission itself and proposes a WD-NS fusion model to interpret the data.

more information:
Jun Yang et al, A long-duration gamma-ray burst of exotic origin, nature (2022). DOI: 10.1038/s41586-022-05403-8

the quote: Deep Space Discovery: Oddball Gamma-ray Burst Forces Review of Theoretical Framework (2022, December 8) Retrieved December 8, 2022 from https://phys.org/news/2022-12-deep-space-discovery-oddball-gamma- ray-theoretical. html

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