Searching for Axion-Like Particles with X-ray Observations of Alpha Centauri

TL;DR

This study searches for axion-like particles (ALPs) in the Alpha Centauri system via X-ray observations, setting new stringent limits on their interactions by detecting no decay signals in the 0.2-10 keV range.

Contribution

It introduces a novel astrophysical search for gravitationally trapped ALPs in a nearby star system, improving constraints on ALP interactions with photons and electrons.

Findings

No ALP decay signals detected in X-ray data.

Established the most stringent limits on ALP interactions to date.

Improved bounds on ALP-photon coupling by about two orders of magnitude at 2 keV.

Abstract

We investigate the production of axion-like particles (ALPs) in stellar cores, where they interact with electromagnetic fields and electrons, with typical masses between $\mathcal O(0.1)$ and $\mathcal O(10)$ keV. These low-energy ALPs are gravitationally trapped in the orbits of stars and subsequently decay into two photons that we detect as monochromatic X-ray lines. We propose to search for these gravitationally trapped ALPs in the Alpha Centauri binary system, our closest stellar neighbor, using sensitive X-ray detectors like Chandra and eROSITA. Our search for ALP decay signals in the energy range of $0.2$ keV to $10$ keV yielded null results, thus establishing the most stringent limits on ALP interactions to date. In the case of ALP-electron coupling $g_{aee}\leq 10^{-15}$, we have improved the limits on the ALP-photon coupling $g_{a\gamma\gamma}$ in ALP mass range between $0.25~\keV$ and $5~\keV$, compared to previous measurements, including those from GW170817, SN 2023ixf, and other sources, and specially the improvement reaches about 2 orders of magnitude at the mass of 2 keV. Even tighter constraints are set for larger $g_{aee}$.