Chandra investigates an X-ray thriller from epic kilonova

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For the primary time, astronomers are finding out the aftermath of a kilonova — an epic burst of power that happens when two neutron stars collide and merge. NASA has used it Chandra X-ray Observatory to watch the kilonova GW170817, and the observations have raised some sudden questions.
Neutron stars are a number of the densest objects within the universe, and after they collide it’s with such pressure that they create ripples in spacetime, referred to as gravitational waves. These gravitational waves have been detected for the primary time in 2017, in a sign referred to as GW170817. Even 4 years later, astronomers have been in a position to see the aftereffects of this occasion within the X-ray wavelength. “Now we have entered uncharted territory right here in finding out the aftermath of a neutron star merger,” mentioned Aprajita Hajela, lead creator of the brand new analysis, in an announcement.
An artist’s conception illustrates the aftermath of a “kilonova,” a robust occasion that occurs when two neutron stars merge. X-ray: NASA/CXC/Northwestern Univ./A. Hajela et al.; Illustration: NASA/CXC/M.Weiss
There was one thing unusual in regards to the X-ray readings from this occasion although. When the merger was first detected, Chandra shortly moved to watch the pair however, regardless of the epic burst of each seen and infrared mild from the collision, there have been no X-rays noticed. However when Chandra appeared once more, 9 days later, it did discover X-rays.
Researchers suppose this might need occurred as a result of the collision brought about jets of X-rays that shot out at totally different angles, which is why Chandra didn’t see them at first as a result of they have been pointed away from Earth. Over time, the jets slowed down and widened out till they turned seen. One other odd discovering was that the X-rays had been getting fainter since 2018, however in March 2020 that stopped and the X-rays remained on the similar brightness. That makes the researchers suppose that the jets aren’t the one supply of X-rays from the merger.
“The truth that the X-rays stopped fading shortly was our greatest proof but that one thing along with a jet is being detected in X-rays on this supply,” mentioned co-author Raffaella Margutti of the College of California at Berkeley. “A totally totally different supply of X-rays seems to be wanted to clarify what we’re seeing.”
There are two doable explanations for this. Both particles from the merger had expanded to the purpose that it has created a shockwave, like a sonic growth. Or it might be that the merger has created a brand new black gap, and the emissions come from materials falling into this black gap. To be taught which of those is right, the researchers will hold each X-rays and radio waves from the supply.
“This could both be the primary time we’ve seen a kilonova afterglow or the primary time we’ve seen materials falling onto a black gap after a neutron star merger,” mentioned co-author Joe Shiny, additionally from the College of California at Berkeley. “Both end result could be extraordinarily thrilling.”

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