A gamma-ray burst (GRB) is always accompanied by a spectacular event, but it typically exists for only a brief moment before disappearing.
Long ago in the universe, a prototype proton star was born. This was heralded by a gamma-ray burst (GRB), followed by a peculiar outburst. Astronomers previously believed that such GRBs occurred due to the formation of a black hole. However, observations by astronomers in the UK regarding this new object indicate that there are multiple ways to trigger a GRB, and many different types of GRBs exist.
Illustration of a gamma-ray burst with the energy of a neutron star. Energy streams erupting from this event. (Photo: Nuria Jordana-Mitjans).
A team of scientists led by Dr. Nuria Jordana-Mitjans from the University of Bath, UK, studied a series of electromagnetic radiation emitted from an object named GRB 180618A.
This object is located on the outskirts of a galaxy approximately five billion light-years away from us and emitted a GRB for a short period, followed by rapid successive emissions that also dissipated quickly.
The entire process originated from the collision of two neutron stars. However, instead of merging to form a black hole, they gave rise to something entirely new. This is the remnant of a neutron star, which is a massive star also known as a proton star.
Dr. Jordana-Mitjans stated, “This is the first time our observations have clearly detected signals from a neutron star that survived for at least one day after the original binary neutron star system perished.”
Aftermath of a Gamma-Ray Burst
Illustration of colliding neutron stars. (Photo: Robin Dienel/Carnegie Science Institute).
A gamma-ray burst is always accompanied by a spectacular event, but it usually exists for only a short time before vanishing. Therefore, astronomers race against time to focus on observing and gathering information about the explosion and capturing its dazzling images before it disappears.
All these results provide clues about the initial cause of the GRB. In the case of GRB 180618A, observations revealed extremely valuable hints.
The mechanical activity and aftermath of this gamma-ray burst are fascinating. It began with two extremely dense progenitor neutron stars spiraling closer together. Eventually, they collided and the explosion erupted.
But just moments before the collision occurred, gravitational waves rapidly radiated outward. When the collision happened, the GRB was triggered. After the two stars merged, the remnant was a rapidly spinning newborn neutron star.
Its radiation provided energy for a hot nebula that is rapidly expanding around the location where the two original stars merged.
The birth of this supermassive neutron star remnant opened a completely new field of study regarding progenitor gamma-ray bursts. Dr. Jordana-Mitjans noted that such discoveries are crucial because they confirm that newborn neutron stars can power some GRBs for a very brief period and emit radiation across the accompanying electromagnetic spectrum.
Decoding the Event
Illustration of a magnetically charged neutron star. (Photo: Carl Knox/OzGrav).
Such short-lived GRBs are intriguing, but we still know little about them. Typically, these events occur when two neutron stars collide, creating an explosion that releases an enormous amount of gamma radiation, and what remains is usually just some type of debris.
The emissions from GRB 180618A indicate that this merger produced an enormous proton star. The subsequent activities were not at all similar to those of most other GRBs. What is certain is that it caused a brilliant flash of light that vanished just 35 minutes later. This duration is quite short compared to some other GRB emissions that last for days or even weeks.
The research team analyzed the data further and discovered that the material emitting the light continued to expand at nearly the speed of light. As it expanded, it cooled down. This explains why it did not last long. However, a larger question arises: what propelled this light to radiate? The answer is the neutron star. This star heated the material of the remnants produced after the collision.
What Comes Next?
When studying GRBs, it is crucial to detect them as quickly as possible. This is the only way to uncover their causes. The flashes emitted from GRBs are extremely rapid, so astronomers must also act quickly to gather sufficient data. Scientists conclude that everything can happen within seconds or minutes. Once the explosion’s location is determined, telescopes can focus on searching for additional supporting signals.
Fortunately, the GRB 180618A research team managed to observe the mid-phase aftermath of the GRB light. They collected data from the Neil Gehrels Swift Observatory at a nearly perfect time.
Professor Carole Mundell from the University of Bath, a co-author of the study, shared: “We are very excited to have captured the optical light right from the onset of this gamma-ray burst. Such an event has been nearly impossible to achieve without robotic telescopes.”
However, when analyzing the collected data, they were astonished to find that this phenomenon could not be explained by the typical black hole-forming GRB model.
This discovery brings new hope for upcoming space surveys using telescopes, and it is possible that we will find signals from hundreds of thousands of “long-lived” neutron stars like this before they decay into black holes.
