Line-profile variations of non-radial adiabatic pulsations of rotating stars III. On the alleged misidentification of tesseral modes

We use a model of a non-radially, adiabatically pulsating rotating star to generate time series of absorption line profiles. We analyse the spectral time series of a tesseral mode with pulsation parameters `=2 andm=−1, to obtain amplitude and phase diagrams as a function of position in the line profile. We investigate whether the phase diagrams can be used to identify the pulsation parameters ` and |m| of this mode. As opposed to the findings of Reid & Aerts (1993), we find that the effects of the Coriolis force do not hinder the identification of the degree ` of the pulsation mode, but that the exact value of i=90◦ that they used does. We show that for an inclination angle just slightly different from 90◦ the chances for an erroneous identification of the degree ` of the `=2,m=−1 pulsation mode, by means of a spectroscopical phase diagram, are very small. We also discuss the interpretation of observed line-profile variations in the Be star η Cen, where a tesseral mode with `=7 andm=|6| might be present.