Line-profile Variability as a Diagnostic for Non-radial Pulsation Mode Identification

Abstract

We use a model of a rotating and adiabatically pulsating star to investigate the observable spectroscopic characteristics of non-radial pulsations. We calculate time series of absorption line profiles in a carefully chosen domain of parameter space.We find that the intensity variations in time series of theoretical spectra, at each position in the line profile, cannot be described by a single sinusoid: at least one harmonic sinusoid needs to be included. Across the line profile the relative amplitudes and phases of these sinusoids vary independently.The blue-to-red phase difference found at the main pulsation frequency turns out to be an indicator of the degree ℓ, rather than the azimuthal order |m|; the phase difference of the variations with the first harmonic frequency is an indicator of |m|.We present linear relations between observable phase differences and the parameters ℓ and |m|. These relations can be used to identify pulsation modes. This method works for spheroidal and toroidal, sectoral and tesseral modes. The method is also applicable to multi-periodic multi-mode pulsations.We apply the method to new data of three rotating β Cephei stars.KeywordsPhase DifferencePulsation FrequencyLine ProfileSectoral ModeAzimuthal OrderThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.