On hydrogen line formation in the atmospheres of pulsating giants.

A method which allows the solution of the transfer equations for an arbitrary velocity distribution has been used to analyze the effects of radial pulsation and shock propagation on the first three hydrogen lines formed in the atmosphere of a 13.3-day W Vir model. The emission component formed behind the shock front is purely thermal, and its strength and frequency position are respectively seen as reflective of the height of the postshock temperature peak and the postshock gas velocity. The absorption component may originate either in the preshock or postshock regions, primarily due to scattering, and causes a discontinuity on the empirical velocity curve under certain conditions.