These massive neutron stars existed in the blink of an eye

Not much can be accomplished in a few hundred milliseconds. But for neutron stars seen in the glow of two gamma-ray bursts, that’s more than enough time to teach us something about the life, death, and birth of black holes. By examining an archive of high-energy flashes in the night sky, astronomers have recently discovered patterns in the light fluctuations left by two different colliding star clusters that show a pause in their journey from the superdense object to the eternal pit of darkness.

This pause — somewhere between 10 and 300 milliseconds — is technically equivalent to two recently formed mega-sized neutron stars, which researchers suspect are each spinning fast enough to briefly delay their inevitable fate as black holes.

“We know that short gamma-ray bursts are produced when rotating neutron stars collide and eventually collapse into a black hole, but the exact sequence of events is not well understood,” says astronomer Cole Miller. University of Maryland, College. Parking in the USA (UMCP).

“We found these gamma-ray patterns in the two flares observed by Compton in the early 1990s.”

For nearly 30 years, the Compton Gamma-ray Observatory has orbited the Earth and collected the glow of X-rays and gamma-rays emitted by distant catastrophes. This high-energy photon archive contains rich data on things like collisions of neutron stars that emit powerful pulses of radiation known as gamma-ray bursts.

Neutron stars are real space monsters. In a volume of space roughly the size of a small city, they have twice the mass of our Sun. Not only does it do strange things to matter by causing electrons to turn into protons, turning them into heavy neutron dust, but it can also create magnetic fields unlike anything else in the universe.

When they return to fast spin, these fields can accelerate particles to ridiculously high velocities, creating polar jets that appear “vibrating” like supercharged beacons. Neutron stars form when more ordinary stars (about 8 to 30 times the mass of our Sun) burn off their remaining fuel, leaving a core with a mass of about 1.1 to 2.3 solar masses that is too cold to withstand its own pressure. Gravity.

Add a little more mass – for example, by squeezing two neutron stars together – and even the weak wobble of their own quantum field can’t resist gravity’s urge for a dead star to crush living physics. Whatever indescribable fear we derive from the dense mass of particles is the heart of a black hole.

The theory underlying the process is pretty straightforward and sets general limits on how heavy a neutron star can be before it decays. For cold, non-rotating balls of matter, this upper limit is slightly less than three solar masses, but it also includes complications that can complicate the journey from a neutron star to a black hole.

For example, at the beginning of last year, physicists announced that they had observed a gamma-ray burst called GRB 180618A, which was discovered in 2018. In the post-flash world, they discovered the signature of a magnetically charged neutron star called a magnetar. a mass close to that of two colliding stars.

Just a day later, this heavy neutron star has now vanished, succumbing to its undoubtedly immense mass, and has become something that not even light can escape from. While its magnetic fields may have played a role, how it managed to resist gravity for so long remains a mystery. These two new discoveries may also provide some clues.

A more accurate term for the pattern seen in gamma-ray bursts recorded by Compton in the early 1990s is quasi-periodic oscillations. The combination of rising and falling frequencies in the signal can be deciphered to identify the final moments of massive objects spinning against each other and then colliding. Each collision produced an object 2.14 times the mass of our Sun, about 20 percent larger than the current record-breaking neutron star pulsar, the researchers can tell. They were also twice the diameter of a typical neutron star.

Interestingly, the objects were spinning at an extraordinary speed of about 78,000 revolutions per minute; this was much faster than the record holder J1748-2446ad, which only made 707 revolutions per second. The few spins that each neutron star manages to complete in its short lifetime (fractions of a second) can provide enough angular momentum to counteract its gravitational bursts. How this might apply to other neutron star mergers, further blurring the line between stellar collapse and black hole formation is a question for future research.