Astronomers have located a rare pattern in the X-ray bursts coming from a neutron-star system no more than 16,300 light-years away.
That star system, MAXI J1621−501, first turned up on 9 October 2017, in data from the Swift or XRT Deep Galactic Plane Survey as a unique point in space flashing unpredictably with X-rays. That was an indication, researchers wrote in a new paper, of a binary system containing a regular star as well as a neutron star or black hole. Both neutron stars and black holes can create unusual X-ray patterns as they absorb matter from their companion stars; however, in very other ways.
In black holes, the X-rays come from matter moving to extreme speeds and generating enormous friction as it falls towards the gravity well. In neutron stars — superdense corpses of giant stars that collapsed; however, haven’t fallen into singularities — the X-rays come from thermonuclear explosions on their outer crusts. Something is inflicting atoms to fuse on the outermost parts of these unusual stars, releasing enormous energies often found deep inside stars (also, in the cores of powerful hydrogen bombs). Some of that power escapes as X-ray light.
The origin of that pattern is not clear. Scientists have merely found about 30 different lights in space that glint this way, the researchers wrote. They refer to patterns like this one as “superorbital periods.” That is since the pattern follows a period that lasts much longer than the binary stars’ orbit around each other, which in the case of MAXI J1621−501 takes 3 to 20 hours.