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, convection in the red giant progenitors of these white dwarfs creates small perturbations in their gravitational quadrupole moment, producing small residual eccentricities.

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See Cohen et al. (2024) for details.