This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Astronomers have linked an X-ray flash discovered by the Einstein Probe to a known type of supernova with unusual features that point to the birth of an ultra-dense, rapidly spinning magnetar. The paper outlining this finding was published in The Astrophysical Journal Letters on July 22.
There is a category of events called extragalactic fast X-ray transients (EFXTs): brief flashes of X-rays lasting minutes to hours whose origins are still poorly understood. A rarer subset, called X-ray flashes, is especially puzzling. Some researchers think they originate from an entirely different kind of dying star.
A few have been directly linked to a visible counterpart in the form of a supernova. Their detection has been difficult because most space telescopes are built to monitor bursts of gamma rays, not lower-energy (softer) X-rays. The Einstein Probe satellite, designed to hunt faint X-ray signals, has been contributing to the growing sample of extragalactic fast X-ray transients and X-ray flashes.
It has found three X-ray flashes corresponding to supernovae so far. In this new study, astronomers led by Gokul P. Srinivasaragavan of the University of Maryland analyzed an X-ray flash, EP250827b, and its supernova counterpart to determine the physical mechanism behind the explosion.
This event, however, was found differently than the three before it. Rather than triggering as an obvious, bright signal, EP250827b appeared as a faint, borderline detection in the Einstein Probe's data. It was too weak on its own to be confirmed as real.
The confirmation came from a separate project pairing the Einstein Probe with the Zwicky Transient Facility (ZTF). It is a ground-based telescope that scans the same patches of sky the Einstein Probe is watching, looking for matching flashes of visible light. ZTF spotted a new optical transient (supernova) in the same location just 5.5 hours after the X-ray flash, confirming the X-ray signal as genuine and giving the event a name: SN 2025wkm.
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