Constraints on the Axion-Photon Coupling Using Stellar Modelling

Abstract

Asteroseismology has been shown to be, together with stellar modelling, an invaluable tool in constraining properties of novel physics. In this work, we study for the first time the influence of axionic production in the evolution of a late main-sequence star, comparing computational models with observational data in order to constrain the axion-photon $g_{a\gamma}$ coupling parameter. We first perform a high-precision calibration of a stellar model to our target star, in order to obtain a benchmark for our other diagnostics. We then apply a two-stage test, first using global quantities and then resorting to precision seismic ratios. We find that seismology allows us to place an independent upper bound of $g_{a\gamma} \leq 0.98\times 10^{-10} $ GeV$^{-1}$ at a $68\%$ confidence level (CL), in the same order of magnitude as both the most recent constraints from the observation of globular clusters and previous bounds obtained through stellar modelling, but more stringent than most current direct axion detections. We also suggest a more conservative limit of $g_{a\gamma} \leq 1.38\times 10^{-10} $ GeV$^{-1}$ at a $95\%$ CL. Moreover, this new diagnostic method can be applied to stellar data that will be obtained in future asteroseismic projects.