Eccentric Pulsars

Pulsars are rapidly spinning magnetized neutron stars that emit a radio beam along their magnetic axis. The beam is detected on Earth as a series of periodic pulses (every time the beam points towards us), like the revolving beacon of a lighthouse.​

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The periodic pulses serve as a very accurate clock, allowing radio observers to detect perturbations due to an orbiting companion star and measure even tiny deviations from a circular orbit, called eccentricities.​

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Pulsars orbiting white dwarfs are expected to have almost circular orbits. However, several recently discovered pulsar-white dwarf binaries are eccentric. The origin of the eccentricity, and why all eccentric systems have orbital periods of about 20-30 days, remains a puzzle.

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See Ginzburg & Chiang 2022 for details.