Axion Helioscopes as Solar Thermometers

TL;DR

This paper proposes a method to use axion helioscopes like IAXO to accurately reconstruct the Sun's temperature profile and other properties in a model-independent way, offering a new astrophysical diagnostic tool.

Contribution

It introduces a novel inversion technique to derive the Sun's radial temperature profile from axion data, demonstrating potential precision and accuracy improvements over existing methods.

Findings

Potential to reconstruct solar temperature up to 80% radius with high accuracy.

Median precision better than 10% in the core region.

Helioscopes outperform neutrino detectors for solar diagnostics.

Abstract

Axions, if discovered, could serve as a powerful new messenger for studying astrophysical objects. In this study we show how the Sun's spatial and spectral "axion image" can be inverted to infer the radial dependence of solar properties in a model-independent way. In particular, the future helioscope IAXO may allow us to accurately reconstruct the Sun's temperature profile $T(r)$ in the region up to about 80% (40%) of the solar radius for an axion-photon coupling $g_{a\gamma\gamma}$ of $6 \times 10^{-11}$ GeV$^{-1}$ ($10^{-11}$ GeV$^{-1}$). The statistical fluctuations in the photon data lead to a median precision of better than 10% (16%) in this region, and the corresponding median accuracy was better than 4% (7%). While our approach can simultaneously infer the radial profile of the Debye scale $\kappa_\text{s}(r)$, its weaker connection to the axion production rate leads to median accuracy and precision of worse than 30% and 50%, respectively. We discuss possible challenges and improvements for realistic setups, as well as extensions to more general axion models. We also highlight advantages of helioscopes over neutrino detectors.