A team of researchers from Northwestern University and the Weinberg College of Arts and Sciences in Germany appears to have stumbled upon a kilonova afterglow, the first of its kind ever observed.
But what exactly is a kilonova?
It is the merger of two neutron stars that generates an explosion 1,000 times brighter than a classical nova. The debris generates visible and infrared light from the decay of radioactive elements such as platinum and gold formed in the debris from the meltdown. This burst of light is called a kilonova.
It was precisely on August 17, 2017, that astronomers observed the first neutron star merger, GW170817 , using light and gravitational waves. GW170817 is an unprecedented opportunity to study the kilonova phenomenon because astronomers observed gravitational waves and electromagnetic radiation from the merger. Since then, researchers around the world have been pointing telescopes on the ground and in space at this event to study it across the electromagnetic spectrum. This is what NASA’s Chandra X-ray observatory has seen.
Chandra is the only observatory that can still detect light from this extraordinary cosmic collision more than four years after the original event.
Something new and extraordinary
Using NASA’s Chandra X-ray Observatory, astronomers observed X-ray emissions from a jet moving very close to the speed of light produced by merging neutron stars. Beginning in early 2018, the X-ray emission steadily faded as the jet continued to slow and expand. They then noticed that from March 2020 to the end of 2020, the decrease in brightness stopped and the X-ray emission was roughly constant in brightness.
“The fact that the X-rays stopped fading rapidly was our best evidence yet that something other than a jet is being detected in the X-rays from this source,” said Raffaella Margutti, an astrophysicist at the University of California, Berkeley. “It seems like a completely different source of X-rays is needed to explain what we’re seeing.”
The researchers think there is likely a kilonova glow or black hole behind the X-rays. Something we have never seen before.
unknown territory
“We have entered uncharted territory in studying the consequences of a neutron star merger. We are seeing something new and extraordinary for the first time. This gives us the opportunity to study and understand new physical processes, which have not been observed before , ”explains Aprajita Hajela, an astronomer at Northwestern University and leader of the work published by The Astrophysical Journal.
To find out what exactly it is, researchers will continue to observe GW170817 using X-rays and radio waves . If it is the afterglow, the X-ray and radio emissions will get brighter over the next few months or years, but if it is a black hole, the X-ray output will decrease over time until no more can be seen. emissions.
Referencia: A. Hajela et al. 2022. The emergence of a new source of X-rays from the binary neutron star merger GW170817. ApJL, in press; arXiv: 2104.02070
