Epoch-dependent absorption line profile variability in lambda Cep

TL;DR

This study analyzes multi-epoch spectroscopic data of lambda Cep, revealing complex, epoch-dependent variability in absorption line profiles that challenges previous pulsation models and suggests a common origin with wind emission variability.

Contribution

It demonstrates that the frequency content of lambda Cep's spectral variability is highly epoch-dependent, indicating a more complex behavior than previously understood.

Findings

No stable pulsation frequency identified across epochs

Variability patterns are similar in wind emission lines and absorption profiles

Frequency content changes significantly from one epoch to another

Abstract

We present the analysis of a multi-epoch spectroscopic monitoring campaign of the O6Ief star lambda Cep. Previous observations reported the existence of two modes of non-radial pulsations in this star. Our data reveal a much more complex situation. The frequency content of the power spectrum considerably changes from one epoch to the other. We find no stable frequency that can unambiguously be attributed to pulsations. The epoch-dependence of the frequencies and variability patterns are similar to what is seen in the wind emission lines of this and other Oef stars, suggesting that both phenomena likely have the same, currently still unknown, origin.