Searching for Axions in the Halo of the Milky Way by Observing Neutron Stars in M4 101 views

Axion dark matter remains a compelling candidate for physics beyond the Standard Model and neutron stars provide highly magnetized environments in which axions may convert into radio photons, allowing for their possible detection. In this work we carry out a search for radio transients consistent with axion-photon conversion in neutron-star magnetospheres within the globular cluster M4. We observe M4 in the L-band with the 20m radio telescope at Green Bank Observatory over eight weeks and analyze the calibrated on-off spectra with a staged candidate-selection pipeline that involves continuum subtraction, threshold-based spike detection, spectral-line matching, and astrophysical plausibility filtering. After subtracting broad continuum structure, we identify narrow residual features above local noise thresholds and compare them against known spectral-line regions and other likely contaminants. Several features remain after this filtering and are retained as candidates for follow-up, though they are not interpreted as detections. Possible alternative origins include statistical fluctuations, residual instrumental systematics, radio-frequency interference, or incomplete spectral-line identification. Future observations and analyses with improved sensitivity, multi-epoch confirmation, and more complete characterization of instrumental and astrophysical backgrounds will be needed to determine whether any of these features are consistent with an axion origin.

BS (Bachelor of Science)

axion; dark matter; globular cluster; radio telescope; Green Bank Observatory

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2026-05-10