Einstein Probe Catches Hidden X-Ray Glow After Neutron Star Merger

A brief flash of gamma rays lasting less than half a second turned out to be only the opening act of a cosmic explosion that astronomers are now studying in a whole new light. According to an international team of researchers, the China-led Einstein Probe captured soft X-ray emission from the same event continuing for nearly ten minutes — a phase of activity that conventional instruments would almost certainly have missed.

The explosion, catalogued as EP250704a in X-rays and GRB 250704B in gamma rays, was observed jointly by the Einstein Probe, the Space Variable Objects Monitor (SVOM) and the Insight-Hard X-ray Modulation Telescope (HXMT), the researchers report. Their findings, published as a cover article in the journal Science Bulletin, suggest the merger of compact objects — most likely neutron stars — leaves behind a central engine that keeps releasing energy long after the initial flash.

The rapidly flickering, colour-shifting X-rays point to continued activity at the heart of the explosion, according to the team. One possible explanation is a newborn magnetar: a rapidly spinning, intensely magnetised neutron star powering the glow. The study was led by An Li of Beijing Normal University and Bin-Bin Zhang of Nanjing University, with the high-energy analysis led by HKU doctoral student Yi-Han Iris Yin as co-corresponding author.

The researchers also conclude that similar hidden X-ray phases may have accompanied earlier short gamma-ray bursts but went undetected, being too soft and faint for previous instruments. The result opens a new window on neutron-star remnants — and could help astronomers pair such flashes with gravitational-wave signals from the same cosmic collisions.

Sources

• Primary: An Li et al., “Minutes-long soft X-ray prompt emission from a compact object merger,” Science Bulletin (2026), DOI: 10.1016/j.scib.2026.08.021
• Phys.org report (Oct 4, 2026)
• ScienMag coverage