About nine days after the collision,took an x-ray signal. According to our understanding of neutron stars, it should have disappeared by now.
But in a new study published Monday in the journal Monthly Notices of the Royal Astronomical Society, researchers examined the effects of a neutron star on a neutron star labeled GW170817 and found that 1,000 days later the X-ray signal was still detectable. .
“We really don’t know what to expect from now on, because all of our models predicted no X-rays,” said Eleanor Troy, an astrophysicist at NASA’s Goddard Space Flight Center and lead author of the study, in a press release.
GW170817 is the first neutron star fusion discovered by the three gravitational wave observatories located on Earth. The triad of observatories was able to triangulate the position of the unification of moments after this happened, allowing researchers to turn their telescopes into space and see the event well. And this is violent.
Since we haven’t seen many collisions with neutron stars (only two have been recorded and confirmed so far), scientists had to rely on models to predict the consequences. For the most part, the models ranked with what was found with the GW170817. When two neutron stars collide, they emit a jet of gamma rays and a huge explosion of bright gas known as a “kilo”. These events are transient – we see them for a few days or weeks and then they disappear. Such was the case with GW170817.
But Chandra, NASA’s X-ray Observatory, still finds X-rays at the site when it focuses on the merger in February, two and a half years after it ignited. Recent measurements show that the signal has faded, but the ghost of an X-ray explosion is still visible and is slightly brighter than the predicted models. Why are these X-rays still visible? This is a puzzle that researchers are trying to solve.
There may be an additional component to neutron star fusion patterns that have not previously been reported. Or maybe the dynamics of the energy released after the collision is a little different from what we expect. An exciting possibility is that the remnants of the fusion are an X-ray neutron star – although much more analysis is needed to determine where the signal is coming from. Astronomers will direct their telescopes to GW170817 in December, providing another opportunity to unravel the mystery of the merger.
“Whatever happens, this event changes what we know about neutron star mergers and the rewriting of our models,” Troy said.