Gamma-ray bursts don’t always come from black holes

November 11 () –

Some short-lived cosmic gamma-ray bursts (GRBs) are triggered by the birth of a supermassive star -a neutron star remnant-and not by a black hole.

Until now, space scientists have largely agreed that the “engine” that drives such energetic, short-lived explosions must always come from a newly formed black hole: a region of space-time where gravity is so strong that nothing, not even light, can escape it.

However, new research from an international team of astrophysicists, led by Dr Nuria Jordana-Mitjans of the University of Bath, challenges this scientific orthodoxy. They publish results in The AstrophysicalJournal.

Dr. Jordana-Mitjans said it’s a statement: “These findings are important, as they confirm that newborn neutron stars can power some short-lived GRBs and the bright emissions across the electromagnetic spectrum that have been detected accompanying them. This discovery may offer a new way to locate fusions of neutron stars, and therefore gravitational wave emitters, when we look for signs in the heavens.”

Much is known about short-lived GRBs. They begin life when two neutron stars, which have been spiraling closer and closer, accelerating steadily, finally collide. And from the crash site, a launched explosion releases the gamma-ray radiation that a GRB produces, followed by a longer lasting glow. A day later, radioactive material that was ejected in all directions during the explosion produces what researchers call a kilonova..

However, precisely what is left after the collision of two neutron stars, the “product” of the collision, and consequently, the energy source that gives a GRB its extraordinary energy, has been a topic of debate for a long time. weather. Scientists may now be closer to resolving this debate, thanks to the findings of the Bath-led study.

Space scientists are torn between two theories. The first theory says that neutron stars merge to briefly form an extremely massive neutron star, only for this star to collapse into a black hole in a fraction of a second. The second argues that the two neutron stars would result in a lighter neutron star with a higher life expectancy.

So the question that has been vexing astrophysicists for decades is this: are short-lived GRBs powered by a black hole or the birth of a long-lived neutron star?

To date, most astrophysicists have supported the black hole theory and there was agreement that to produce a GRB it is necessary for the massive neutron star to collapse almost instantaneously.

Astrophysicists learn about neutron star collisions by measuring the electromagnetic signals from the resulting GRBs. The signal originating from a black hole would be expected differ from that coming from a neutron star remnant.

The electromagnetic signal from the GRB explored for this study (called GRB 180618A) made it clear to Dr. Jordana-Mitjans and her colleagues that a neutron star remnant, rather than a black hole, must have given rise to this outburst.

Elaborating, Dr Jordana-Mitjans said: “For the first time, our observations highlight multiple signals of a surviving neutron star that lived for at least a day after the death of the original neutron star binary.”