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 ${\gamma }_t$→${\gamma }_l$+a and in the plasma coalescence process ${\gamma }_t$+${\gamma }_l$→a, where ${\gamma }_t$ and ${\gamma }_l$ are transverse and longitudinal plasmons, respectively. The previously discussed ${\gamma }_t$→${\gamma }_t$+a is kinematically suppressed. It is shown that a previous calculation of the Primakoff emission rate already includes these effects if T≫${\omega }_0$ (plasma frequency ${\omega }_0$) so that astrophysical bounds on the axion-photon coupling remain unchanged.