Fast X-ray transients shine light on how stars end their lives and the distant universe

A new type of stellar explosion provides a new way to probe the distant universe, according to new results published today in Natural astronomy.

Researchers from the University of Lancaster have joined a world team, led by Radboud University, in the Netherlands, examining “Fast-ray transient (FXTS)” which are very mysterious explosions of X-ray, which generally lasts a few minutes.

“We know that these unique explosions have existed for some time, but it is only now, thanks to the new Mission of the Einstein probe, that we can identify them in almost real time,” said astronomer professor Peter Jonker, of Radboud University, Netherlands, discoverer of one of the first events of this type, and second author of the document of today.

The authors used a precise position provided first by an X -ray space telescope, the Einstein probe, and refined on the ground by the Atlas optical telescope to identify the rapid transitional of X -rays in space by observations with the very large telescope in Chile and the conventional telescope in Spain.

“These observations show that this explosion occurred when the universe was less than 10% of its current age – the light has been going to us for 12 billion years,” said Professor Andrew Levan, of Radboud University, and the first author of the study.

“The combination of distance and brightness means that this explosion has gone more energy in a few seconds than the sun over its life.

“These extreme energies, as well as the detection of the gamma rays by the Fermi satellite, suggest that the rapid X-rays transients are linked, at least sometimes, with the extremely powerful gamma rays that have been studied for half a century.”

“A real question is whether all the rapid X -ray transients come from gamma radiography type systems, or if there is much more diversity. Our article shows that many of them could be gusts of gamma shelves, but there are good reasons to think that there is still much to discover,” added Professor Jonker.

During the examination of the observations of the very large telescope, it became clear that there are very few materials, in particular hydrogen, surrounding this burst.

Hydrogen acts as a filter for ultraviolet light, blocking it through the universe.

However, in the history of the universe, at the time of this rapid transitory with X -rays, the universe underwent its last global change in a process called reionization, where hydrogen between the galaxies was affected by ultraviolet and “reionized” light.

The challenge is that almost all of the ultraviolet light created by the stars of the universe is blocked by hydrogen in the galaxy in which it is.

“Our observations show that perhaps 10% of the ultraviolet light created in the host galaxy of the rapid X-ray transitional escapes to ionize the universe,” said Andrea Sacardi, CNE stock market to CEA Paris-Saclay, and the third author of the article.

“This is the furthest event where we can directly see the light escape from the stars. Galaxies like this are probably really important for reionization.”

These observations are one of the first events detected by the Einstein probe.

“During the year since this first object that we found and studied 20 others of these explosions, they are up to their promise as a new exciting way to explore both how the stars put an end to their lives, and also what the universe looked like in a distant past,” added Professor Levan.

The co-author of research and lecturer in astrophysics from the University of Lancaster, Dr. Samantha Oates, was part of the research team.

She said: “This event is new and interesting because only a handful of FXT was discovered until very recently, and their origin was a mystery, mainly because they had been found in archival observations.

“As they were discovered, it was too late to follow up on these transient X -ray objects at other wavelengths to obtain other information on what could cause it.”

The Einstein probe, launched in January 2024, is, explains Dr. Oates, revolutionizing the detection and monitoring of FXTS, which are now regularly detected, and the community is alerted quickly, allowing rapid follow -up.

She added: “The Einstein probe has opened a new window on the universe, allowing us to probe the origin of these phenomena of transient X -rays and to expand our knowledge of the behavior associated with the death of massive stars.”