X-ray and gamma-ray pulsations identify Geminga as a neutron-star pulsar

What changed

An X-ray observation identified coherent pulsations with a period near 237 milliseconds from the source associated with Geminga. A subsequent EGRET analysis found gamma-ray pulses at the same period, linking the earlier high-energy gamma-ray source to a pulsar. A later NASA account reproduces a pulse-phase profile from the gamma-ray observations and attributes the X-ray and gamma-ray measurements to different teams.

Scientific scope

An X-ray observation identified coherent pulsations with a period near 237 milliseconds from the source associated with Geminga. A subsequent EGRET analysis found gamma-ray pulses at the same period, linking the earlier high-energy gamma-ray source to a pulsar. A later NASA account reproduces a pulse-phase profile from the gamma-ray observations and attributes the X-ray and gamma-ray measurements to different teams. Halpern and Holt reported the soft X-ray pulsations; the gamma-ray timing analysis belongs to a different team. Geminga’s gamma-ray source had already been observed. The period derivative printed in the later NASA account is inconsistent with the original literature and is not used here. Pulsar properties depend on the timing interpretation.

Evidence

The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. Halpern and Holt reported the soft X-ray pulsations; the gamma-ray timing analysis belongs to a different team. Geminga’s gamma-ray source had already been observed. The period derivative printed in the later NASA account is inconsistent with the original literature and is not used here. Pulsar properties depend on the timing interpretation.

Contributors

• The named authors in the research record · SCIENCE: These are the listed authors of the cited contribution sources. Paper authorship does not quantify individual effort. An incomplete list is explicitly marked; same names are not automatically merged.

• Gamma-Ray Astrophysics: New Insight into the Universe, Second Edition
• Discovery of soft X-ray pulsations from the γ-ray source Geminga

Provisional WRS assessment, edition 2026-10-28.1. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.

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