Axions in Andromeda: Searching for Minicluster -- Neutron Star Encounters with the Green Bank Telescope

TL;DR

This study used the Green Bank Telescope to search for radio signals from axion minicluster and neutron star encounters in Andromeda, setting constraints on axion properties but finding no candidate signals.

Contribution

It introduces a novel radio transient search method for axion miniclusters using the GBT and applies it to the Andromeda galaxy.

Findings

No candidate signals detected above 5σ threshold.

Sensitive to axion masses between 33 and 42 μeV.

Developed a new observation and analysis strategy for axion searches.

Abstract

The QCD axion and axion-like particles are compelling candidates for galactic dark matter. Theoretically, axions can convert into photons in the presence of a strong external magnetic field, which means it is possible to search for them experimentally. One approach is to use radio telescopes with high-resolution spectrometers to look for axion-photon conversion in the magnetospheres of neutron stars. In this paper, we describe the results obtained using a novel approach where we used the Green Bank Telescope (GBT) to search for radio transients produced by collisions between neutron stars and dark matter clumps known as axion miniclusters. We used the VErsatile GBT Astronomical Spectrometer (VEGAS) and the X-band receiver (8 to 10 GHz) to observe the core of Andromeda. Our measurements are sensitive to axions with masses between 33 and 42 $\mu$eV with $\Delta$$m_a$ = 3.8$\times10^{-4}$ $\mu$eV. This paper gives a description of the search method we developed, including observation and analysis strategies. Given our analysis algorithm choices and the instrument sensitivity ($\sim$2 mJy in each spectral channel), we did not find any candidate signals greater than 5$\sigma$. We are currently implementing this search method in other spectral bands.