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arXiv · 2504.04209

Axion Superradiance in Dipole Magnetic Fields of Pulsars

Topi Sirkiä·Matti Heikinheimo·Kimmo Tuominen
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Abstract

We consider constraints on the axion-photon coupling by superradiance due to a plasma instability in the magnetospheres of millisecond pulsars. We compute the growth rate of a superradiant axion cloud in a dipole magnetic field, and give a semi-analytical formula for the superradiance rate for the lowest state. By requiring the associated instability time to be longer than the characteristic age of the supermassive black-widow millisecond pulsar PSR J0952-0607, we examine the pulsar-timing array constraints on axions of mass $\sim 10^{-12}\text{ eV}$. We find that competitive axion bounds from plasma instabilities are unlikely unless a new high spin pulsar is discovered.

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Topi Sirkiä, Matti Heikinheimo, Kimmo Tuominen. 2025-04-05. Axion Superradiance in Dipole Magnetic Fields of Pulsars. https://arxiv.org/abs/2504.04209

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