A Gamma-Ray Burst Showed Up Without the Gamma Rays

Something exploded in deep space on March 5, 2024. China's Einstein Probe caught it mid-flash: two X-ray flares, back to back, 200 seconds apart. Then the telescopes looked for the gamma rays. There weren't any.

The object, designated EP240305a, fits the profile of a gamma-ray burst almost perfectly. Two-peak structure, X-ray timing, radio afterglow that decayed like a textbook jet expanding into space. Gamma-ray bursts are among the most energetic events in the universe, typically spawned when massive stars collapse or compact objects merge. The signatures all lined up, except the one the explosion is named after.

Researchers pointed instruments across X-ray, optical, near-infrared and radio wavelengths at the source for weeks. The X-rays dropped by four orders of magnitude within 21 days. The radio emission evolved from a compact, self-absorbed state to an optically thin one over roughly two months, consistent with a discrete jet ejection expanding outward. A faint infrared candidate counterpart faded and disappeared. None of it pointed anywhere definitive.

The team ruled out the usual suspects methodically: tidal disruption events fade over months, not days; stellar flares don't sustain radio emission for weeks; magnetar giant flares peak in under a second. What's left is a gamma-ray burst that either fired its jet at an angle away from Earth, dimming the gamma-ray signal below detection, or choked the jet before it broke through, producing the X-ray and radio fingerprint of a GRB without the part that usually gets it named.

The authors call it, carefully, "a gamma-ray dark GRB-like transient." Which is a precise way of saying: we know what this looks like, and we cannot tell you what it is.

Read the full story at Live Science, June 13, 2026

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