Plasmon decay into low-mass bosons in stars

A low-mass boson a, if it couples by a two-photon vertex, can be produced in the plasma decay process ₓ₋+a and in the plasma coalescence process ₓ+₋, where ₓ and ₋ are transverse and longitudinal plasmons, respectively. The previously discussed ₓₓ+a is kinematically suppressed. It is shown that a previous calculation of the Primakoff emission rate already includes these effects if T₀ (plasma frequency ₀) so that astrophysical bounds on the axion-photon coupling remain unchanged.