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Enlarge / Artist’s content of GRB 211211A. The kilonova and gamma-ray burst is connected the right.
Aaron M. Geller/Northwestern/CIERA
A twelvemonth ago, astronomers discovered a almighty gamma-ray burst (GRB) lasting astir 2 minutes, dubbed GRB 211211A. Now that antithetic lawsuit is upending the long-standing presumption that longer GRBs are the distinctive signature of a monolithic prima going supernova. Instead, 2 autarkic teams of scientists identified the root arsenic a alleged "kilonova," triggered by the merger of 2 neutron stars, according to a new paper published successful the diary Nature. Because neutron prima mergers were assumed to lone nutrient abbreviated GRBs, the find of a hybrid lawsuit involving a kilonova with a agelong GBR is rather surprising.
“This detection breaks our modular thought of gamma-ray bursts,” said co-author Eve Chase, a postdoc astatine Los Alamos National Laboratory. “We tin nary longer presume that each short-duration bursts travel from neutron-star mergers, portion long-duration bursts travel from supernovae. We present recognize that gamma-ray bursts are overmuch harder to classify. This detection pushes our knowing of gamma-ray bursts to the limits.”
As we've reported previously, gamma-ray bursts are highly high-energy explosions successful distant galaxies lasting betwixt specified milliseconds to respective hours. The archetypal gamma-ray bursts were observed successful the precocious 1960s, acknowledgment to the launching of the Vela satellites by the US. They were meant to observe telltale gamma-ray signatures of atomic weapons tests successful the aftermath of the 1963 Nuclear Test Ban Treaty with the Soviet Union. The US feared that the Soviets were conducting concealed atomic tests, violating the treaty. In July 1967, 2 of those satellites picked up a flash of gamma radiation that was intelligibly not the signature of a atomic weapons test.
Just a mates of months ago, aggregate space-based detectors picked up a powerful gamma-ray burst passing done our star system, sending astronomers worldwide scrambling to bid their telescopes connected that portion of the entity to cod captious information connected the lawsuit and its afterglow. Dubbed GRB 221009A, it was the astir almighty gamma-ray burst yet recorded and likely could beryllium the "birth cry" of a caller achromatic hole.
There are 2 types of gamma-ray bursts: abbreviated and long. Classic short-term GRBs past little than 2 seconds, and they were antecedently thought to lone hap from the merging of 2 ultra-dense objects, similar binary neutron stars, producing an accompanying kilonova. Long GRBs tin past anyplace from a fewer minutes to respective hours and are thought to hap erstwhile a monolithic prima goes supernova.
Enlarge / This Gemini North image, superimposed connected an representation taken with the Hubble Space Telescope, shows the telltale near-infrared afterglow of a kilonova produced by a agelong GRB.
Int'l Gemini Observatory/NOIRLab/NSF/AURA/NASA/ESA
Astronomers astatine the Fermi and Swift telescopes simultaneously detected this latest gamma-ray burst past December and pinpointed the determination successful the constellation Boötes. That speedy recognition allowed different telescopes astir the satellite to crook their attraction to that sector, enabling them to drawback the kilonova successful its earliest stages. And it was remarkably adjacent for a gamma-ray burst: astir 1 cardinal light-years from Earth, compared to astir 6 cardinal years for the mean gamma-ray burst detected to date. (Light from the astir distant GRB yet recorded traveled for immoderate 13 cardinal years.)
“It was thing we had ne'er seen before,” said co-author Simone Dichiara, an astronomer astatine Penn State University and a subordinate of the Swift team. “We knew it wasn’t associated with a supernova, the decease of a monolithic star, due to the fact that it was excessively close. It was a wholly antithetic benignant of optical signal, 1 that we subordinate with a kilonova, the detonation triggered by colliding neutron stars.”
As 2 binary neutron stars statesman circling into their decease spiral, they nonstop retired almighty gravitational waves and portion neutron-rich substance from each other. Then the stars collide and merge, producing a blistery unreality of debris that glows with airy of aggregate wavelengths. It's the neutron-rich debris that astronomers judge creates a kilonova's disposable and infrared light—the glow is brighter successful the infrared than successful the disposable spectrum, a distinctive signature of specified an lawsuit that results from dense elements successful the ejecta which artifact disposable airy but lets the infrared through.
Enlarge / When neutron stars merge, they tin nutrient radioactive ejecta that powers a kilonova signal. A precocious observed gamma-ray burst turned retired to awesome a antecedently undetected hybrid lawsuit involving a kilonova.
Dreamstime
That signature is what consequent investigation of GRB211211A revealed. And since the consequent decay of a neutron prima merger produces dense elements similar golden and platinum, astronomers present person a caller means of studying however these dense elements signifier successful our universe.
Several years ago, the precocious astrophysicist Neil Gehrels suggested that longer gamma-ray bursts could beryllium produced by neutron prima mergers. It seems lone fitting that NASA's Swift Observatory, which is named successful his honor, played a cardinal relation successful the find of GRB 211211A and the archetypal nonstop grounds for that connection.
“This find is simply a wide reminder that the Universe is ne'er afloat figured out,” said co-author Jillian Rastinejad, a Ph.D. pupil astatine Northwestern University. “Astronomers often instrumentality it for granted that the origins of GRBs tin beryllium identified by however agelong the GRBs are, but this find shows america there’s inactive overmuch much to recognize astir these astonishing events.”
DOI: Nature, 2022. 10.1038/s41550-022-01819-4 (About DOIs).
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