NASA/CXC/M. Weiss
In 2017, astronomers discovered a phenomenon known as:kilonova: Merger of two neutron stars accompanied by powerful bursts of gamma rays. Three and a half years later, astrophysicists have discovered a mysterious X-ray that they believe could be the first detection of a “post-kilonova glow,” as astrophysicists said could be the first observation of the matter. that fall into the black hole that formed after merging.
Such as inform us earlier, DISCOVER LIGO by gravitational waves laser interferometry† This method uses powerful lasers to measure small changes in the distance between two objects miles apart. (LIGO has detectors in Hanford, Washington, and in Livingston, Louisiana. A third detector, known as Advanced VIRGO, was commissioned in Italy in 2016.) Three detectors allow scientists to determine the source of any night chirps.
In addition to seven binary black hole mergers, discover the second round of LIGO, from November 30, 2016 to August 25, 2017, Binary fusion between neutron stars Once gamma ray burst and signals in the rest of the electromagnetic spectrum. The event is now known as GW170817. These signals include telltale signs of heavy elements – particularly gold, platinum and uranium – that resulted from the impact. Most of the lighter elements form in the suffocating explosions of massive stars known as supernovae, but astronomers have long believed that heavier elements may originate in kilonovae from the collision of two neutron stars.
Kilonova’s discovery in 2017 provided evidence that these astronomers were right. The recording of this type of celestial event was unprecedented, and it solemnly marked the dawning of a new era in the so-called “Multiple Astronomy Messages† †
Since then, astronomers have been searching for a matching optical signature when LIGO/VIRGO picks up a gravitational wave signal from neutron star mergers or potential mergers between neutron stars and a black hole. The assumption was that black hole and black hole mergers would not yield an optical signature, so there was no point in looking for a signature – until 2020. Then astronomers discovered it. first guide for such a phenomenon. Astronomers made the discovery by combining gravitational wave data with data collected during an automated sky survey.
But Kilonova’s 2017 film remains unique, according to Abrajita Hajela, lead author of the new paper and a graduate student at Northwestern University. Hajela Calls Kilonova “The only event of its kind” and “a treasure chest of several scenes for the first time in our field”. Along with other astronomers from Northwestern University and the University of California, Berkeley, I have tracked the evolution of GW170817 since it was first discovered by LIGO/Virgo using a spacecraft. Chandra X-ray Observatory†
NASA/CXC/NGST (Public Domain)
Chandra first detected X-ray and radio emissions from GW170817 two weeks after the merger, which lasted 900 days. But those first X-rays, driven by jets of fusion at nearly the speed of light, began fading out in early 2018. From March 2020 through the end of that year, the sharp drop in brightness stopped and X-rays became steady, somewhat in terms of brightness.
To help solve the mystery, Hajela and her team collected additional observational data from both Chandra and Very Large Array (VLA) in December 2020, 3.5 years after the merger. It was Hajela who woke up at 4 am to the news of a surprisingly strong and bright X-ray – four times higher than would currently be expected if the emissions were powered by the aircraft alone. (The VLA detected no radio emissions.) These new emissions remained constant for 700 days.
This means that for them a completely different source of X-rays must be the source of energy. One possible explanation is that expanding debris from the merger triggered a shock wave, similar to a sonic boom, as well as jets. In this case, the merging neutron stars cannot instantly collapse into a black hole. Instead, the stars are spinning fast for a second. This rapid spin would have countered the gravitational collapse briefly enough to produce a rapid tail of Kilonova’s heavy projectiles, which unleashed the shock wave. As those heavy projectiles slowed down over time, the shocks converted their kinetic energy into heat.
‘Fall in. It’s finished.’
“If the merging neutron stars collapsed directly into a black hole without an intermediate phase, it would be very difficult to explain the excess X-rays we see now, because there would be no solid surface for the objects to bounce back as they flew at velocities around these auroras. Co-author Raffaella Margutti said: from the University of California at Berkeley. “Fall in. It’s finished. The real reason I’m scientifically excited is that we might see more of the plane. Maybe we finally get some information about the new compact object.”
Brian Metzger of Columbia University has proposed an alternative scenario: X-rays could be caused by material falling into the background ray formed during fusion. This is also the first scientific finding, Hagel said, because this kind of long-term buildup hasn’t been seen before.
More views are planned from now on and this data will help solve the problem. If X-rays and radio waves brighten in the coming months or years, they will confirm the Kilonova-Aurora scenario. If the X-ray emission decreases sharply or remains constant, with no accompanying radio emission, this would confirm the black hole accretion scenario.
Anyway, “This will be the first time we see a kilonova auroras or the first time we see matter falling into a black hole after a neutron star merger,” Co-author Joe Bright said:Postdoctoral fellow at the University of California, Berkeley. “Neither outcome would be very exciting.”
DOI: The Astrophysical Journal Letters, 2022. 10.48550 / arXiv.2104.02070 †About DOIs†
