Astronomers have reported the discovery of an unusual X-ray transient detected by the Einstein Probe that does not fit any known class of cosmic explosions. The paper presenting its multiwavelength analysis was published in the journal Monthly Notices of the Royal Astronomical Society on June 13.

On March 5, 2024, a space telescope called the Einstein Probe—designed to scan the sky for sudden X-ray flashes—caught a brief, never-before-seen source called EP240305a. It produced two brief X-ray flares, one right after the other, separated by about 200 seconds of quiet.

Researchers quickly pointed several telescopes at this source to gather more data in X-rays, infrared, optical and radio wavelengths; the analysis of these multiwavelength data is presented in the new study.