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

We employ an asteroseismic model of L19-2, a relatively massive (Msstarf ~ 0.75 M?) and hot (Teff ~ 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 (? ~ 113 s and ? ~ 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 ma cos2s lesssim 25 meV or an axion-electron coupling constant of gae lesssim 7 × 10-13.