1994/10/03 by G. Raffelt, Georg G. Raffelt, A. Weiss +1 · 5 citations
Physics and Astronomy · #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #hep-ph
paper · pdf · doi:10.1103/physrevd.51.1495
published as Phys.Rev.D51:1495-1498,1995 · 11 pages, uuencoded and compressed postscript file
arxiv created 1994/10/03 · openalex publication_date 1995/02/15 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
If axions or other low-mass pseudoscalars couple to electrons (``fine structure constant'' \mathrm\ensuremathαa) they are emitted from red giant stars by the Compton process \ensuremathγ+e\ensuremath→e+a and by bremsstrahlung e+(Z,A)\ensuremath→(Z,A)+e+a. We construct a simple analytic expression for the energy-loss rate for all conditions relevant for a red giant and include axion losses in evolutionary calculations from the main sequence to the helium flash. We find that \mathrm\ensuremathαa\ensuremath≤0.5\ifmmode×\else\texttimes\fi10^\mathrm\ensuremath-26 or ma\ensuremath≤9 meV/cos2\ensuremathβ lest the red giant core at helium ignition exceed its standard mass by more than 0.025 scrM_\mathrm\ensuremath\bigodot, in conflict with observational evidence. Our bound is the most restrictive limit on \mathrm\ensuremathαa, but it does not exclude the possibility that axion emission contributes significantly to the cooling of ZZ Ceti stars such as G117-B15A for which the period decrease was recently measured.