2025/07/29 by Zhou, Yu, Liu, Jiejia, Takhistov, Volodymyr +1
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.2507.22006
Axion-like particles (ALPs) provide a compelling avenue for exploring physics beyond the Standard Model. In astrophysical magnetized plasmas an ALP-photon coupling gaγ induces energy-dependent oscillations in the photon survival probability that imprint modulations on emission spectra. X-ray observations of bright spectrally-smooth sources can provide particularly sensitive probes of ultralight ALPs with masses ma \lesssim 10-11 eV due to long propagation distances, strong magnetic fields and high photon statistics. We present a comprehensive forecast of ALP-photon conversion in three representative systems: (i) background active galactic nuclei (AGNs) observed through foreground intracluster magnetic fields, (ii) central AGNs within their host cluster halos and (iii) Galactic X-ray binaries viewed through the Milky Way field. Using detailed simulations we assess the prospective sensitivity of high-resolution X-ray missions including XRISM, Athena, and Arcus. For typical magnetic field configurations a 5 Ms XRISM observation of the Perseus Cluster AGN NGC 1275 can reach down to gaγ ∼ 3 × 10-13 GeV-1 at ma \lesssim 10-12 eV, while Athena's superior energy resolution improves this reach by a factor of ∼ 3. We quantify the impact of magnetic field modeling, photon statistics, and spectral binning strategies. Our results demonstrate the scientific potential of high-resolution X-ray observations to probe photon-ALP coupling in previously inaccessible parameter space, offering a powerful window into physics beyond the Standard Model.