Deep Photospheric Emission Lines as Probes for Pulsational Waves

Weak line emission originating in the photosphere is well known from O stars and widely used for luminosity classification. The physical origin of the line emission are NLTE effects, most often optical pumping by far-UV lines. Analogous lines in B stars of lower luminosity are identified in radially pulsating $\beta$ Cephei stars. Their diagnostic value is shown for radially pulsating stars, as these lines probe a much larger range of the photosphere than absorption lines, and can be traced to regions where the pulsation amplitude is much lower than seen in the absorption lines.