SIMBAD references

If axion-like particles (ALPs) exist, photons can convert to ALPs on passage through regions containing magnetic fields. The magnetized intracluster medium of large galaxy clusters provides a region that is highly efficient at ALP-photon conversion. X-ray observations of active galactic nuclei (AGNs) located within galaxy clusters can be used to search for and constrain ALPs, as photon-ALP conversion would lead to energy-dependent quasi-sinusoidal modulations in the X-ray spectrum of an AGN. We use Chandra observations of the central AGN of the Perseus Cluster, NGC 1275, to place bounds on massive ALPs up to m_ a_ ∼10^–11 eV, extending previous work that used this data set to constrain massless ALPs.