Constraining the Axion-Photon Coupling with Massive Stars

TL;DR

This paper uses the evolution of 8-12 solar mass stars to set new constraints on the axion-photon coupling by analyzing the impact on the blue loop phase, which is observable in Cepheid stars.

Contribution

It introduces a novel stellar evolution method to constrain axion-photon interactions using the blue loop phase in massive stars.

Findings

Sets an upper bound g_{Aγγ} < 0.8×10^{-10} GeV^{-1} on axion-photon coupling.

Demonstrates the blue loop phase's sensitivity to axion energy losses.

Provides constraints comparable or better than existing bounds.

Abstract

We point out that stars in the mass window ~ 8-12 Msun can serve as sensitive probes of the axion-photon interaction, g_{A\gamma\gamma}. Specifically, for these stars axion energy losses from the helium-burning core would shorten and eventually eliminate the blue loop phase of the evolution. This would contradict observational data, since the blue loops are required, e.g., to account for the existence of Cepheid stars. Using the MESA stellar evolution code, modified to include the extra cooling, we conservatively find g_{A\gamma\gamma} <~ 0.8 * 10^{-10} GeV^{-1}, which compares favorably with the existing bounds.