An asteroseismic constraint on the mass of the axion from the period drift of the pulsating DA white dwarf star L19-2

TL;DR

This study uses asteroseismic observations of the white dwarf L19-2 to place new constraints on axion properties, suggesting possible axion-induced cooling effects in the star.

Contribution

It provides the first asteroseismic constraint on axion mass and coupling from pulsating white dwarf data, indicating potential axion emission.

Findings

Hints of extra cooling compatible with axion emission

Axion mass constrained to less than 25 meV

Axion-electron coupling constant limited to below 7×10^{-13}

Abstract

We employ an asteroseismic model of L19-2, a relatively massive ($M_{\star} \sim 0.75 M_{\sun}$) and hot ($T_{\rm eff} \sim 12\,100$ K) pulsating DA (H-rich atmosphere) white dwarf star (DAV or ZZ Ceti variable), and use the observed values of the temporal rates of period change of its dominant pulsation modes ($\Pi \sim 113$ s and $\Pi \sim 192$ s), to derive a new constraint on the mass of the axion, the hypothetical non-barionic particle considered as a possible component of the dark matter of the Universe. If the asteroseismic model employed is an accurate representation of L19-2, then our results indicate hints of extra cooling in this star, compatible with emission of axions of mass $m_{\rm a} \cos^2 \beta \lesssim 25$ meV or an axion-electron coupling constant of $g_{\rm ae} \lesssim 7 \times 10^{-13}$.