SIMBAD references

Axion-like particles (ALPs) can induce localized oscillatory modulations in the spectra of photon sources passing through astrophysical magnetic fields. Ultra-deep Chandra observations of the Perseus cluster contain over 5×10⁵ counts from the active galactic nucleus (AGN) of the central cluster galaxy NGC1275 and represent a data set of extraordinary quality for ALP searches. We use this data set to search for X-ray spectral irregularities from the AGN. The absence of irregularities at the O (30 % ) level allows us to place leading constraints on the ALP-photon mixing parameter g_aγγ_ 1.4–4.0×10^–12 GeV^–1 for m_a 10^–12 eV, depending on assumptions on the magnetic field realization along the line of sight.