Surface emissivity of optically thick, magnetized plasma, and the luminosity of accreting neutron stars

The total energy flux F radiated per unit area of optically thick, isothermal (at x-ray temperatures T) plasma in a strong magnetic field B is calculated for a medium that is either homogeneous or has an electron density N increasing exponentially inward. Analytic F(T, B, N) relations are obtained for some limiting cases. For the customary plasma parameters adopted for accreting neutron stars, the dominance of scattering over absorption makes the plasma emissivity decidedly lower than the blackbody value (F<>kT) the flux increases with the field strength (FproportionalN/sup 1/2/T/sup 5/4/B, FproportionalT/sup 7/6/B/sup 4/3/, respectively), ultimately approaching F/sub T/. These results are germane to observed pulsar and burster x-ray luminosities L. The L(T) relations predicted by several x-ray pulsar models are compared against the observations