Deep Photospheric Emission Lines as Probes for Pulsational Waves

TL;DR

This paper explores how weak photospheric emission lines in B stars, especially in pulsating $eta$ Cephei stars, serve as probes for pulsational waves, revealing deeper stellar layers than absorption lines.

Contribution

It demonstrates the diagnostic potential of photospheric emission lines in pulsating stars, expanding their use beyond traditional absorption line analysis.

Findings

Emission lines probe larger photospheric regions.

Lines trace regions with lower pulsation amplitudes.

Enhanced understanding of stellar pulsation mechanisms.

Abstract

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.