Projected bounds on ALPs from Athena

Abstract

Galaxy clusters represent excellent laboratories to search for Axion-Like Particles (ALPs). They contain magnetic fields which can induce quasi-sinusoidal oscillations in the X-ray spectra of AGNs situated in or behind them. Due to its excellent energy resolution, the X-ray Integral Field Unit (X-IFU) instrument onboard the Athena X-ray Observatory will be far more sensitive to ALP-induced modulations than current detectors. As a first analysis of the sensitivity of Athena to the ALP-photon coupling $g_{a{\hat{I}}^3{\hat{I}}^3}$, we simulate observations of the Seyfert galaxy NGC1275 in the Perseus cluster using the SIXTE simulation software. We estimate that for a 200ks exposure, a non-observation of spectral modulations will constrain $g_{a{\hat{I}}^3{\hat{I}}^3}\lesssim 1.5\times 10^{-13}{\mathrm{GeV}}^{-1}$ for $m_a\lesssim 10^{-12}\mathrm{eV}$, representing an order of magnitude improvement over constraints derived using the current generation of satellites.

5 pages, 3 figures. Accepted to MNRAS