A team of international astrophysicists has made a significant breakthrough in understanding fast X-ray transients (FXTs), mysterious bursts of X-rays that have puzzled astronomers for decades. Led by Northwestern University and the University of Leicester, the researchers used a combination of ground-based telescopes and space-based instruments to study the closest FXT associated with a massive star’s death.
The team discovered that the FXT was produced by a “failed” jet, which is a jet of high-energy particles that did not break through the outer layer of the dying star. Instead, it remained trapped inside, emitting lower levels of energy that can be detected as X-rays.
This finding bridges the gap between FXTs, gamma-ray bursts (GRBs), and supernovae, providing new insights into the physics behind these cosmic explosions. The researchers used data from the Einstein Probe space-based instrument to capture the most nearby FXT ever observed, located 2.8 billion light-years away from Earth.
The study also confirmed that a broad-lined Type Ic supernova was responsible for the observed X-ray signal. This type of explosion is typically associated with highly energetic events like GRBs, but in this case, evidence of a GRB was missing.
The discovery has significant implications for our understanding of stellar explosions and the diversity of cosmic events. The team’s findings will be published in two companion studies accepted by The Astrophysical Journal Letters.
“Through decades of scientific study, we know that jets can successfully plow through a dying star’s outer layers,” said Northwestern’s Jillian Rastinejad. “In our study, we found this ‘trapped’ jet outcome is more common in massive star explosions than jets that successfully emerge from the star.”
The research was supported by several organizations, including the European Space Agency and NASA. The findings mark a significant step in understanding the complex landscape of cosmic explosions and will likely lead to further breakthroughs in the field.
Source: https://news.northwestern.edu/stories/2025/07/supernovas-trapped-jet-reveals-source-of-fast-x-ray-transient