In late August, an instrument on the International Space Station, referred to as NICER, noticed its brightest burst of X-ray radiation but.
NICER, or the Neutron Star Interior Composition Explorer, research X-rays that come from neutron stars, the super-dense remnants of some stars after they go supernova. This explicit burst got here from a neutron star referred to as SAX J1808.
The burst was extraordinarily energetic, releasing about as a lot power in 20 seconds because the solar does in 10 days. Aside from being extremely vivid, the burst had a mixture of options that astronomers hadn’t seen collectively in a single occasion. This made the occasion a priceless alternative to review and higher perceive the physics behind these X-ray bursts. A staff of astronomers that studied the burst reported its findings in a latest paper in The Astrophysical Journal Letters.
NICER Neutron Stars
NICER observes X-ray bursts from neutron stars in binary methods the place a neutron star and one other object orbit one another. SAX J1808, for instance, is partnered with a brown dwarf, an object someplace between a star and a fuel big planet.
The neutron star pulls hydrogen fuel from the companion object right into a swirling disk round it. These gases can even fall inward from disk to neutron star, generally triggering explosions that detectors like NICER see as bursts of X-rays.
In the August burst, the astronomers noticed proof that the explosion blew materials off of the neutron star in two layers. A layer of hydrogen was possible ejected first, adopted by a layer of helium. NICER had beforehand seen neutron stars give off X-ray bursts that corresponded to both hydrogen or helium layers, however not each in a single burst like this, mentioned Peter Bult, an astronomer at NASA’s Goddard Space Flight Center and one of many authors of the paper.
A Mysterious Brightening
Another function the astronomers noticed was fluctuations in brightness all through the burst. This was most likely from the neutron star rotating in order that hotter and cooler sides of it confronted the detector. They additionally noticed one thing for which they don’t but have a proof: SAX J1808 obtained brighter once more after the primary a part of the burst.
Seeing proof for a number of phenomena occurring in a single occasion means the researchers can examine whether or not they’re associated.
“I’m most excited by the fact that we see these various phenomena in the same burst,” Bult mentioned. “I think with this burst, we might have a really good shot of getting more into the specifics of what might cause this re-brightening.”