Constraints on axion-like particles from non-observation of spectral modulations for X-ray point sources

We extend previous searches for X-ray spectral modulations induced by ALP-photon conversion to a variety of new sources, all consisting of quasars or AGNs located in or behind galaxy clusters. We consider a total of seven new sources, with data drawn from the Chandra archive. In all cases the spectrum is well fit by an absorbed power-law with no evidence for spectral modulations, allowing constraints to be placed on the ALP-photon coupling parameter g a γγ . Two sources are particularly good: the Seyfert galaxy 2E3140 in A1795 and the AGN NGC3862 within the cluster A1367, leading to 95% bounds for light ALPs ( m a ≲ 10 −12 eV) of g a γγ ≲ 1.5 × 10 −12 GeV −1 and g a γγ ≲ 2.4 × 10 −12 GeV −1 respectively.