By studying the signal of GW170817 from the merger of two neutron stars and the result, among other things, in a kilonova, a team of astronomers indicates the unique nature of this phenomenon, including the residual X-ray flux likely to provide clues to the nature of the object resulting from the merger of these two The two huge stars.
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Discovered on August 17, 2017 in galaxy NGC 4993 through tools lego And the Virgin (Two interferometers are designed to detect gravitational waves), GW170817 is a reference attributed to the direct observation ofgravitational waves. They are described as oscillations in curvature Free time Gravitational waves propagated from a source, Albert predicted Einstein As early as 1916, but it took nearly a hundred years for the first observation of gravitational waves to be made, in September 2015.
Unique Signal
according to astrophysiciststhis signal could have been emitted after fusion between two neutron stars. But what makes it special is its discoveryElectromagnetic waves Associated with it: This is the first time that an astronomical phenomenon has been detected in the form of gravitational waves as well as in the form of light. In fact, a wince The gamma (GRB170817A), associated with GW170817, was detected by Fermi Gamma Ray Space Telescope Less than two seconds after the start of the gravitational wave signal.
Since then, nearly 70 observatories, on Earth or in space, have taken part in observing this phenomenon. The radio telescopes American VLA And the VLBA, for example, were able to observe the waves radio Residues associated with GW170817, confirming an A . scenario fusion two neutron stars.
Kilonova is related to this phenomenon
Detected approximately 11 hours after gravitational waves were observed, the AT 2017gfo event was interpreted as a kilonova (It can be defined as a Supernova under the light). Due to its spatial and temporal proximity to GW170817, this kilonova was associated with the same neutron star merger. This phenomenon was accompanied by jets of charged particles moving at a Speed Near light and production episode X-rays, measured by NASA’s Chandra Observatory. According to a team of American astrophysicists, the study of these X-rays could be the key to identifying the object resulting from the merger of these two neutron stars.
Shortly after its discovery, X-ray emissions are emitted by an aircraft Thing It will diminish little by little, while the flow of matter has slowed down. But since 2020, this drop in brightness It will stop, giving way to a relatively constant X-ray emission. according to Astronomy scientiststhen this indicates the discovery of an additional body, different from a charged particle jet: another X-ray source is thus required to explain these observations.
Twilight… or even a black hole?
According to astronomers, this new source of X-rays could come from a shock from the rapid expansion of debris from the merger between the two stars. This shock would have heated up the surrounding material, and thus would emit X-rays – this phenomenon would then be associated with the remaining kilonova brilliance.
hypothesis Black hole It was also not excluded, because material falling into this cosmic giant can similarly generate X-ray emissions, since the accompanying radiation should be much brighter.
To find the end of the story, the Astronomy scientists They will continue their observations of GW170817, in X-rays as well as in radio waves: in the case of the remaining luminosity of Kilonova, X-ray emissions and radio waves are expected to increase over the next few months. On the other hand, if the emission of X-rays decreased and the emission of radio waves stopped, scientists would instead lean towards a formation scenario. Black hole (This would then be the lowest mass detected!).
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