Spectroscopic Nonadiabatic Observables as a New Tool for Mode Identification in β Cep Stars

Abstract

AbstractWe present a new method of mode identification based on the line profile variations. We calculate time series of Si III 455.26 nm for models of β Cep stars with a mass of 10 M⊙. The Spectroscopic observables are amplitude ratio and phase difference for various oscillation parameters derived from the line profile changes. Based on the computed values we plot diagrams to search for the best discriminators of modes.In most Spectroscopic diagrams the unstable modes are grouped in well-defined regions with different m-values, and a few of them give also separation with respect to l-values. Moreover, on the basis of almost all of the diagrams we can distinguish the prograde modes from the retrograde ones, and the zonal modes from those with m ≠ 0.In this paper we discuss also the influence of the inclination angle, the amplitude of the radius variation and the equatorial velocity on the diagnostic values of the Spectroscopic diagrams.