X-ray afterglow of the kilonova was explained by the action of a shock wave

(ORDO NEWS) — Before merging and flaring up the kilonova GW170817, neutron stars described a short spiral, giving rise to a shock wave, the consequences of which astronomers are still observing.

In 2017, scientists for the first time recorded a gravitational wave burst that arose from the merger of a pair of neutron stars.

Having localized the GW170817 signal in space, this region was also studied using conventional telescopes. Thus, the hypothesis was confirmed that in such catastrophes – outbreaks of kilonovae – the nuclei of the heaviest chemical elements, including gold, uranium and platinum, are born.

GW170817 is still emitting X-rays, and recently American astronomers have associated it with shock waves that arose during the merger.

Researchers continue to observe the afterglow of GW170817, including with the help of the Chandra space telescope operating in the X-ray wavelength range. The remnants of the kilonova radiated in x-rays for the first 900 days after the outbreak, throwing out into space narrow and ultrafast plasma streams – jets.

Then this glow began to weaken until it reached a plateau, where it stabilized. Finally, at the end of 2020, it again jumped at times, once again gaining a foothold at a new level for a long time. Jets cannot explain this.

Astronomers associated such jumps in the X-ray afterglow of GW170817 with a shock wave that arose during a kilonova outburst. Before merging and forming (most likely) a black hole, neutron stars converged in a short and swift spiral.

This did not last long, only a second, but during this time large volumes of matter were ejected from the system at high speed. The plasma tail, driven by the flash, created a shock wave, which, slowing down, gives off excess energy, radiating in the X-ray range.

“If the merged neutron stars immediately collapsed into a black hole, it is impossible to explain the excess X-ray emission, because there is no surface from which the matter could repel and fly away at high speed. It would just fall inside, and that’s it, ” explained Raffaella Margutti, one of the authors of the new work.


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